Baton Rouge, Louisiana: A Southern city with a dark and gothic history. An epidemic of serial killers between 1994 and 2003 had the people of the city looking over their shoulders in terror and panic.

"In a 10-year period, we've had five serial killers in Baton Rouge," said Premila Burns, former first assistant district attorney of East Baton Rouge Parish, Louisiana.

This sadistic madman was at large and had been tormenting cops for quite a while. His string of horrific attacks began in the 1990s, and police believe a single psycho killer is behind all the carnage.

Nightly newscasts reported the discovery of more women stabbed, strangled, raped and murdered.

"He would rape each of these women, and then to cover it up, beat them to death, stab them to death," said Prem Burns.

But one victim escapes, and she points a finger at a mentally challenged convicted voyeur named Derrick Todd Lee. DNA evidence ties Lee to the rapes and murders of at least seven women.

Cops have their serial killer, and the people of Baton Rouge breathe a sigh of relief. But the nightmare is not over.

Cops soon learn there's a new serial killer on the loose, and he's even worse.

"A true serial killer: taking souvenirs, dismembering victims," said Prem Burns.

"You're talking about someone that's sexually deviant," said Former Senior FBI Criminal Profiler Mary Ellen O'Toole.

His calling cards were far more brutal, gruesome and cruel than Baton Rouge had ever seen before.

"They were all really petite women," said Burns. "It was very obvious that he chose women that he could handle."

And all also linked by a distinctive and grisly manner of death.

"All of the victims were killed by use of nylon zip-ties," said East Baton Rouge Sheriff's Major Bryan White.

The killings begin again with the discovery of Katherine Hall, found at the end of a dark, rural road, nude, strangled, her body hacked and sliced to the bone. And chillingly, Hall's body was found displayed beneath a street sign in a twisted parody of death.

"She was on her back in a kind of balletic pose next to a 'dead end' sign, which I thought was a his humor, in a very sick kind of way, 'dead end,'" said Burns.

"He had sex with his victims after they were dead," said Major Bryan White.

"Very close examination of her mouth showed that there was a pubic hair with a root ball, which allows full DNA testing," said Burns.

"Immediately they said this is not a normal heat-of-the-moment homicide," said Major White. "We knew we had a problem."

The problem escalated when the killer ups his ante with another murder even more vicious and gruesome.

"Johnnie Mae Williams, face down in the woods, decomposing, covered up, you could barely tell it was a human being," said Burns.

Williams, 45, had been strangled to death, her body laid out for maximum horror.

"He obviously had posed her looking for the shock factor, because her legs were sliced down the back and on the front pretty good," said White.

But Williams' killer wasn't done with her, even after her death.

"She had her arms folded up under her," said White. "When she was rolled over her arms fell out, and it was at that point that we saw that her hands had been cut off.

"He was getting more and more bold and brazen I guess since he had gotten away with it this long," said White.

But that "bold and brazen" act gave up another genetic sign of her killer.

"Even though her hands had been cut off, they looked at the bones and a human hair was found, and it was a body hair, and they could tell it was from a Caucasian male," said Burns.

Several months later, the butcher strikes again. Donna Johnston is found.

"She had a tattoo of a butterfly on her leg and after she was dead, he cut that off," said White.

"She fought with him and we know she fought with him because his DNA was under the fingernails of her right hand," said Burns. "She only had one hand left because he amputated her left arm right below the elbow."

Detectives are armed with a load of DNA evidence, but the DNA profile doesn't match anyone in the system.

Investigators scan every blade of grass around Donna Johnston's body, looking for additional evidence.

"It was actually a cow pasture where she was dumped and there were some ruts where vehicles had been passing back and forth, and really very significant-looking tire tracks," said White. "So we did tire castings. It was a Goodyear tire."

"Every victim was found totally nude, no identification near them, making it very hard to find their identity," said Prem Burns.

An eagle-eyed investigator spots a clue, embedded in the soft ground near where Donna Johnston's body was found: fresh tire tracks.

"That is what I call 'gumshoe police work,'" said Burns. "He looked at those tire tracks, took pictures, made casts of it and he would not let it go."

Cops catch a break when the tracks come back. The tire is very rare.

"We do a little research and there's literally only maybe a couple hundred sets of these particular tires sold in the entire Baton Rouge area," said Bryan White.

Now they've just got to match them and hope they lead to the serial killer. Major Bryan White dispatches his task force, talking to everyone who purchased these tires in the last 12 months.

"That information was divided up into leads for us to go to these people's houses and ask them, do they still have a vehicle with those tires," said White.

But White also needs a swab of DNA from the people who bought those tires. Detectives have already gathered DNA samples from the victims -- from Katherine Hall's mouth, the bones of Johnnie Mae Williams' severed arms, and under the fingernails of Donna Johnston's one remaining arm. But none of the samples match anyone currently in the DNA database.

A tire might place a car in that field -- but DNA could tie the victims to their killer.

"We asked them if they would voluntarily submit to an oral DNA swab," said White. "A lot of people were like 'I've never killed anyone, sure I will,' but that's ultimately what lead us to Sean."

Sean Vincent Gillis is one of those 200 tire owners in the area. Gillis is unemployed, soft-spoken and intelligent, living in a home owned by his mother. He has no criminal history, and by all accounts is just a run-of-the-mill, mild-mannered science fiction geek.

But it's what he says to the detective at his door that sounds an alarm.

"Very suspicious statements," said White. "Johnnie Mae Williams was a friend of his -- 'Oh, as a matter of fact, she's ridden in my vehicle before, she's been in my home, you know, I used to pay her to clean my house.'"

Gillis even admitted being near the crime scene, and offered a strange excuse as to why his tire tracks were in that field when police ask him to come down for what they called "a little friendly Q and A" that was recorded by investigators.

Sean Vincent Gillis: "I had had some beer and needed to go to the bathroom real bad, and I knew I wasn't gonna make it to the house. You know what I'm saying, my bladder was -- how they put it, Cheech and Chong put it one time -- 'My eyes are floating.' That's how it felt."

And if cops should find any blood in his car? Gillis has an excuse for that too.

Gillis: "About a month after we got the car, she got her period. She had her period and it just soaked, I mean it's like I said, it looked like a massacre in that front seat."

"He said 'Man, blood just started flying everywhere in the vehicle,'" said White. "And Max said 'Well let me ask you this then: Is there any reason that blood could be in the back seat?'"

Gillis: "There shouldn't be, I mean barring wind blowing, you know. I'm not saying you're not going to find one of Johnnie's hairs back there, but you shouldn't finda anything from anyone else."

"He said 'Yeah I think the windows were down and probably some blood flew out the window and got blown back in.' And everyone at that time looked and said 'It's him,'" said White.

Detective: "I'll be right back, OK?"

Gillis: "So much for 'a little friendly Q and A.'"

"When he made that statement, at that point I turned to one of our detectives, and said 'Draft a search warrant for his vehicle right now,' and we did," said White.

Analyzing Gillis's cheek swab is now top priority.

"We called the crime lab and said 'This DNA swab we're bringing you, put whoever you've got to put on it, but if you could expedite, we think we have our guy,' and they started working on it immediately," said White.

But the lab would have to work fast. Even with the tire match and Gillis's outrageous statements, cops can't hold him.

"We had some very incriminating statements but it was all circumstantial," said Bryan White.

What if Gillis takes off? Or worse, what if the stress drives Gillis to kill again? Cops are now secretly tailing Sean Vincent Gillis's every move.

"Then we just went and waited for crime lab results," said White.

It was one of the longest nights of the detective's life.

Detectives believe Sean Vincent Gillis is the serial killer they've been hunting. But while his DNA is being processed, they have to let him go back to the home he shares with Terri Lemoine.

Sean Vincent Gillis didn't feel much like talking anymore once detectives turned up the heat during his interrogation.

"Right after that Sean kind of started getting irritated, he said 'Look guys,' he said 'I haven't killed anyone. You told me if I came when I was ready to come home, you'd bring me home, I want to go home. I'm ready to go," said Bryan White.

Without lab results tying him to the crimes, cops have no choice but to cut Gillis loose.

Then after several excruciating hours of waiting, the phone rings.

"When they called that night, they said 'It's him,'" said Major Bryan White. "We had him."

The next call White makes is to a judge to get a warrant for Gillis's arrest.

"Soon as the warrants were signed, the SWAT team made preparations to hit his house, and they hit it shortly thereafter," said White.

Cops swarm Gillis's home, and they're in for a shock. The killer doesn't live alone.

"I think he was found in bed with Terri," said White.

Gillis's girlfriend Terri Lemoine. Lemoine says she had no idea why a SWAT team is busting down her door.

"I'm yelling 'What's going on? What's going on?' And I look at Sean, and Sean just shrugged his shoulders and said 'Sorry honey-bunny,'" Terri Lemoine tells Crime Watch Daily. "And one of the officers turns around and looks at me and says 'Didn't you know you're living with a serial killer?' The whole world came tumbling down that night."

It's a seemingly quiet world Terri Lemoine had shared with Sean Vincent Gillis for nine years -- a long time since Terri, a convenience store clerk, first laid eyes on the shy, quirky Gillis.

"My best friend walks in and says 'Sean, this is Terri, Terri this is Sean. Y'all have everything in common, you have to get to know each other,'" said Lemoine. "We both loved science fiction, we both loved 'Star Trek,' we both loved collecting things."

At first there's no clue to what Gillis really liked to collect.

"He was cute in a little teddy-bear sort of way, the type of person you'd want to bring home to mom, actually," said Lemoine.

Platonic dating leads to Lemoine moving in to Gillis's dilapidated house, where things -- according to Terri Lemoine -- stayed platonic.

"Sean didn't believe in sex," said Lemoine. "I asked him about it one time and he told me that he had been taught that it was a nasty thing, and that he shouldn't do that.

Lemoine still worked at the convenience store. Gillis's only job was picking her up after her shift. There's often odd behavior, but Gillis again always has an excuse.

"One morning he came and picked me up and the car had an awful odor in it, and I was so tired, and I was like 'What is that smell in the car?' And he said he had hit an animal on the way picking me up," said Lemoine. "Came home, I came inside, went to bed, he went to washing the car."

Lemoine also notices Gillis is racking up a lot of miles on the car.

"Well I got kind of concerned and wanted to know who he was driving around with. I thought he was [cheating]," said Lemoine. "I found out from the police that he was hunting. Looking basically for someone to kill."

Now nine years later, surrounded by cops and with her boyfriend in handcuffs, Terri Lemoine still can't believe it.

"When everything happened, I laughed at the police when they told me why they arrested him," said Lemoine. "I literally laughed and told them 'Boy, do you have the wrong house.' They said he admitted it and at which point my mouth just dropped and I said 'Well, I'll have to ask him myself.'"

Warning: Graphic details ahead.

Terri Lemoine was convinced cops have her boyfriend all wrong.

"I never saw anything bad about him," said Lemoine.

So she went to get the truth straight from Gillis himself.

"I just walked in to the police station and picked up the little phone and asked, I just said 'Sean, did you do everything that these police officers said you did?' And again, the little thing with the head. Drops his eyes and says 'Yeah, sorry honey-bunny, again,' and I just got up and turned around and walked out," Terri Lemoine tells Crime Watch Daily.

Lemoine isn't the only one to hear Sean Vincent Gillis come clean.

Sitting for hours in a cramped interrogation room, cops hear every sick secret come spilling out.

Sean Vincent Gillis: "I'm sorry I hurt people. But I would do it again."

"Once he started confessing, he confessed. He laid it out A to Z," said Major Bryan White.

Gillis: "If anything in my useless life comes out, help the little girls today not to be the premature corpses of tomorrow."

"It was just like something clicked in Sean's brain, because at some point he looked at me and said 'Hey, you got a pencil?' I said "Sure," and he started rapping them off," said White. "He started naming other victims, he said 'Get ready.' He admitted to the three that we had him on, and he admitted to five more."

Unsolved murders that had stumped detectives for years: Hardee Schmidt; Joyce Williams; Lillian Robinson; Marilyn Nevils; and 81-year-old Ann Bryan.

"I was shocked at some of the names he threw out there," said Bryan White.

Where Gillis goes next is terrifying. In chilling, matter-of-fact detail, he recounts his ritual after Terri Lemoine left for the night shift.

Gillis: "You let me out on the street, I'll find somebody before sundown."

Hunting women, strangling and mutilating them, then using their bodies for unspeakable acts of sexual gratification.

Detective: "When you say hunting, what do you mean?"

Gillis: "I was strictly going out looking for a victim."

Gillis's prey? Prostitutes, drug addicts, anyone who looked helpless or willing to get into his car.

"Disposable people. People that society would not miss," said former prosecutor Prem Burns. "He considered them to be worthless."

Gillis: "Even beat to death looks better than the photo you got of her right there."

Once inside his car, Gillis wasted no time in brandishing his crude instrument of death.

Gillis: "A white nylon tie lock, we're talking two and a half feet long at least, just make a loop and you've got a few inches to spare. I slip it on her head. 'Too bad,' you know, and pulled."

Detective: "You remember her saying anything to you during this fight?"

Gillis: "Other than a lot of, 'No more,' you know, 'Why are you doing this?' And I really didn't have an answer for her other than, you know, "I'm killing you,' you know?"

Then, in detail that is hard to stomach, Gillis casually explains what he did after the bodies went cold.

Gillis: "Pretty much brought her back home from there. To my house."

Like a macabre erotic shower with the body of Donna Johnston.

Gillis: "I held her up, bathed her, held her to me, you know."

Detective: "So you put soap on her and stuff too?"

Gillis: "Yeah, I mean, we were taking a shower, you know?"

Giving a manicure to the severed hands of Johnnie Mae Williams.

Gillis: "I painted her nails while I had her hand in there."

And even more disturbing, while his girlfriend Terri Lemoine is at work, Gillis performs a deranged autopsy of Joyce Williams right on the kitchen floor.

Gillis: "She had beautiful legs. That's one thing that I recall about her, and I wanted to keep those legs. I like a good set of gams, good set of legs. Looking at it, just the curvature of it, it was beautiful. You know, notwithstanding it was cut off of a person."

"When they sprayed the baseboards of his kitchen with Luminol, the baseboards under the cabinets, that it just lit up like a Christmas tree," said White. "Said he decapitated her right there."

Gillis: "At that point I pretty much moved on to the head."

Detective: "The same knife?"

Gillis: "The same knife. It went through the throat just like that. It was like cutting butter."

Gillis's computer delivers even more evidence of his ghoulish trophy hunting.

"During the search of his house and his computer was seized, he had taken one of his victims out to a dump and staged his own crime scene," said White. "Took pictures of the victim in the trunk of his vehicle and he captured the greater portion of his license plate in the picture, and it was still on his computer."

Former Senior FBI Criminal Profiler Mary Ellen O'Toole is face to face with Gillis, and sees his secrets go even deeper. The seed of Gillis's depravity was planted early.

"One of his paraphilic behaviors was necrophilia, and manifested itself probably before 10," said O'Toole.

Behavior that continued with a sexual fascination with his mother.

Mary Ellen O'Toole: "Did you ever think about having sex with her?"

Gillis: "Yes, of course. She's not an unattractive woman, even if you see her and meet her now. I've thought if she passed away, y'all would find me in bed with her."

Now, with Gillis himself admitting every gruesome detail, this case is locked up.

Or is it?

Right from the start, before his confessions even begin, Gillis was savvy enough to say this:

Gillis: "You know, I think I really should have brought a lawyer."

With that comment comes a big problem. The information that he provided to the police after he asked for an attorney was not permissible in court.

Without those videotaped confessions, prosecutors were sweating: Would an admitted serial killer slip through their fingers?

All those fears are put to rest just as Gillis's trial is set to begin.

"I'll never forget this. I was in the courtroom and one of the female deputies went and just kind of nudged me after a hearing in this case, and hands me a letter from Tammie saying, 'I need to give you these, and they're the letters put on a silver platter for me," said former prosecutor Premila Burns.

Those letters are from Tammie Purpera, a friend of Gillis's final victim, Donna Johnston. Purpera had been corresponding with Sean Vincent Gillis in jail.

"And I went 'Bingo! Bingo! That's another nail in his coffin,'" said Burns. "She said 'I never thought he would answer me. Honest to goodness I never thought he'd be so stupid to answer me.'"

But Gillis does answer, and within those letters was a written confession. Gillis details Donna Johnston's last moments from the eyes of her killer.

He writes "Your friend died quickly." "She was so drunk it only took about a minute and a half to succumb to unconsciousness and then death. Honestly, her last words were 'I can't breathe.' Yours, oh so beyond sorry, Sean Vincent Gillis.'"

"So that letter gave us our first-degree murder beyond any doubt whatsoever," said Burns.

Purpera's letters also give the trial one of its most dramatic moments.

Prosecutor Premila Burns has the jury stop and watch the clock for 90 excruciating seconds. In the letters Gillis wrote, that's how long it took Donna Johnston to die.

Sadly, Tammie Purpera would never see it played out in court.

"Tammie ended up getting cancer, Tammie died before the trial. And it's like, she still did it," said Burns. "Even in death, Donna's friend came through by just writing those letters to him and getting those answers and giving them honestly to me and not asking a thing in return."

With the overwhelming evidence, including DNA and now Gillis's own self-incriminating letters, the verdict is undeniable: Guilty of first-degree murder. Gillis is sentenced to three life terms in prison.

"I think if Sean had not been apprehended, he would have continued to kill," said Mary Ellen O'Toole.

At Gillis's house in a quiet neighborhood, a magnolia tree blooms in the front yard. Inside is where some of the most unspeakable acts played out on a kitchen floor.

Believe it or not, Gillis's girlfriend Terri Lemoine still lives here.

"The police told me that he had dismembered one of his victims in the kitchen," Lemoine tells Crime Watch Daily when we visited her at the house. "Literally right there. I would say in those four squares right there."

Do you ever have feelings while you're standing here at the kitchen sink and think back to the horrible things that happened here?

"No," said Lemoine. "That would be like thinking 'I can't live on this piece of property because there was a war here.' It's a building. That's the way I look at it."

And the memories of madness aren't confined to the house. Gillis's blood-soaked car that he nicknamed "Buffy" after the TV show "Buffy the Vampire Slayer," still sits rotting in Terri Lemoine's back yard.

Do you think you're going to end up selling this to someone who has like a morbid collection of things having to do with serial killers?

"I have no idea. I've thought of donating the thing. The company that I bought it from, they didn't want it back because they said it was a biohazard," said Lemoine. "And I've never bothered myself with it, actually."

You still live in the house and you still have the car. Why?

"The house didn't do anything wrong. I mean, what was left of what he did has been disposed of. It's been taken away," said Lemoine.

So you don't feel a bad or a negative energy in this house?

"No. Too much good has happened since," said Lemoine.

After he went to jail what did you do?

"I redid the floors and redid some of the walls," said Lemoine.

Prosecutor Prem Burns says all the remodeling in the world will never erase the horror that Sean Vincent Gillis inflicted on eight innocent people, their families and the city of Baton Rouge.

"This was like a walking piece of evil hunting and preying after other human beings," said Burns. "Those women had more life and more worth in them than he will ever have if he lives to be 100 years."