>> this is "nightline." tonight -- >> i like to use a knife. a gun is too noisy. >> he's called the most notorious serial killer in the country. >> first time i killed somebody, it was such a rush. >> addicted to murder. inside the mind of a monster. and selfiesnafu. flirting with asking out an underaged fan. now, the damage control. >> i used bad judgment and i learned my lesson. >> plus, they might be the cutest animals ever. the search of these rare and cuddly creatures. but first, the "nightline" top 5 which starts right now.

>> good evening and thanks for joining us. tonight we take you inside the mind of one of the most evil men in america. he's a notorious and admitted serial killer, and the last 48

hours, his story has come to a dramatic conclusion. we got a rare and chilling interview with him for our series, crime and punishment. >> first time i killed somebody, it was such a rush. >> tommy lynn sells, a man who says he belongs on death row. >> i was raised to do time. i wasn't raised to live out there in that world. >> sells was convicted of killing 13-year-old katie harris, stabbing her to death in her bedroom. >> i like to use a knife. a gun is too violent, too noisy. it just wouldn't fit my hand well. >> and later, he admitted to killing dozens more. so many, he can't even keep track. >> i'm not making notches on my holster. i knee it's been a lot.

>> addicted to killing is the way he characterized it. >> i don't have an on and off switch. i'm just after that drug. i'm after that feeling. >> "nightline" interviewed sells on death row in 2010. one of the rare glimpses into the mind of a serial killer. >> it's complicated. when people enter my life, they get hurt. >> the drifter's vagrant lifestyle helped him elude police for nearly 15 years as victims turned up from coast to coast. >> when you look at me, you know what hate is because i don't know what love is. two words i don't like to use is love and sorry. because i'm about hate. >> his methods for killing were as random as the people he targeted. he raped many before cutting their throats or beating them. stabbing others. he strangled some.

>> a lot of jerking, a lot of movement. it's a physical -- you become part of it. >> and described it all with seeming detachment from the horrors h ecaused. >> i don't have no feelings no more. no emotion, no -- >> and no remorse. >> i liked to watch the eyes paid, the pupil fade. it's just like setting their soul free. >> we asked sells what would happen if we said something that angered him. >> if he was in a fight and, you know, smash your head down in the concrete, so be it. but what do you think happens? it cracks like a coconut. >> how did he become this monster? sells blames much of his murderous range on sexual abuse he says he suffered as a child. >> i think every time i killed that guy that molested me all them years.

i seen that in my mind over and over. >> yet, children were among his victims. >> i didn't want them to live through the pain i lived through. >> i tried to get in this door right here. >> it was katie harris' murder that finally ended his killing spree. a few days later, tommy lynn sells walked police through his crime spree. >> i lifted the window up and that's how i got in. >> kids stayed up a little later and we got a in a little fight about where we were going to sleep. we talked about the time brittany spears and n sync. crystal is one of his few survivors. she was sleeping over at katie's house that night. more than a decade later, it's all still sfresh in her memory. >> i woke upstartled a little bit out of nowhere and i was kind of confused to a lot of noise.

>> i woke this girl up. >> her friend katie was asleep on the bottom bunt bunk. >> i cut her bra. >> i could see there was a scary older man that i have never seen before. >> i stabbed her here and she jumped back and i cut her like this right here. >> he had a hand on her mouth and on her neck. she was looking at me, he cut her throat and fell to the ground. >> 13-year-old katie harris lay dying on the floor. >> he was about to shut off the light, he noticed one more time that i was there, he just shut the door and came back towards me with the knife. >> the only thing he said was move your hands. he reached over the top of me and cut my neck. >> she severed her windpipe.

>> i am very sure he thought he killed me. >> crystal identified tommy lynn sells as the assailant. >> to be honest, he seemed blank. i mean, there was no emotion. >> they lack conscious, they lack remorse, they lack guilt. that's one of the reasons why they terrorize society so much. >> experts say sells offers a textbook example into the mind of a serial killer. he's been studying how and why the adorable little boy pictured here turned into brutal killers. could it have been the makeup of their brains? >> biology coming together with environmental insults which raised the odds of an individual becoming a violent criminal offender. >> recent researchers sulg that psychopath thi may actually be

evident in the brain and that a simple brain scan could reveal key differences in the minds of serial killers. >> the advent of molecular gin nettics, we've been able to peer into the minds of murderers for the first time. >> but for some of the families of his victims, ending that brain function was important. sells was on death row for more than 13 year, the most recent delay, over the exact makeup of the drug cocktail that would be used to kill him. sells said the pain of the death penty paled in comparison to his life. >> i suffer more here than i'll ever suffer in that grave. when they kill me, i'll be free

then. >> last night, he was executed at 6:27 p.m. >> when asked if he wanted to make a last statement, he simply answered no. >> for the family of katie harris, it was long overdue. >> now it's a day of closer and celebration. justice has been served. >> a brave young woman we heard from there. we'll be right back. what's a powerful way to cut through everyday greasy messes? [ male announcer ] sponges take your mark. ♪ [ female announcer ] one drop of ultra dawn has twice the everyday grease cleaning ingredients of one drop of the leading non-concentrated brand... ♪ [ crowd cheering ] ...to clean 2x more greasy dishes. dawn does more. so it's not a chore.

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>> is there an animal cute enough people will travel all

over the world to see? lemures may look like stuffed animal, but there's much more nan meets the eye. >> i defy you to not immediately fall in love with them. this is the lemur. they come in more than 100 flavors. there another the dancing lee mur, the ring tail remur, and the black and white lemur. they only live in one place on earth, the country of madagascar off the coast of africa. this place and these animals are now the subject of a new imax movie called island of lemurs. it's an exceedingly difficult place to film, especially given the elaborate equipment necessary for an i max movie.

with no roads, the director used a hot air balloon to get some shots and forced scores of locals to carry their gears around. >> two or three steps off the pathway and you can't find the pathway anymore. >> reporter: but for all the difficulties, the shots they captured, amaze. like this lemur, famous for its loud cry. >> it's really the pop star of the lemur. it's like air horns suddenly blasting off at you. >> one of the stars of the movie is dr. patricia wright, an american primatologist who once spent months searching for the greater baboon lemur. >> there he was, feasting on

crunchy young bamboo shoots. >> one of the things she loved about lemurs, the females are in charge. >> the females sits where she wants to sit, leads them where she wants to lead them. and she's the boss. >> what was it like having an imax team follow you around? >> i thought they would be terrifie terrified? but no. a crane would go up and they would kind of look at it and they wouldn't run away. >> i can personally attest to the lemur's agreeable nature. a few years ago, i went to m madagascar myself. they always look slightly horrified. watch out. he likes my camera. i even got to see the dancing lemurs up close. this is why they call them dancing lemurs. but to see one of the more rare and adorable of all, we were

told we needed to travel all the way up to the northern part of the country into a towering and dauntingly beautiful landscape that looks like a set from jurassic park. >> this is supposed to be the most beautiful lemur in the world? >> it was a long slippery hike that involved an unfortunate number of leeches. . >> finally, we saw them. they looked like cotton balls with tails. >> they are two lemurs. they're quite beautiful as prommed. and they don't seem to mind at all that we're here. actually, there are three, four.

>> in fact, there were seven in this family. they spend their days eating, grooming, scampering and playing. >> we're pretty close to them. we get very close. >> yeah. >> they're not afraid of people. there's not many predators so they're not scared of us? >> yeah, exactly. >> not many predators here, but there is real danger to all of the lemurs of the madagascar. illegal loggers have been pillaging the forest the lemurs need to survive. >> how much trouble is the lemur in right now? >> the lemur is in big right now. 91% of them are endangered of extinction. >> our oldest ancestor now under threat from the most dangerous primate of all -- man. do you hope the movie can make a

big difference? >> i think the movie is going to make a great difference. right now, nobody knows what the lemur. but once you see the movie is out there, you see how beautiful they move and how beautiful they are, i think everyone is going to want to save lemurs. >> so the dance of the lemur can carry on. i'm dan harris in new york. >> the i ma, movie is now in theatres. next, james franco's social media scandal with a teenage girl. ♪ ♪ ♪ [ male announcer ] the nissan altima with nasa inspired zero gravity seats. ♪ let it take the weight off your drive.

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sometimes celebrities forget everything on social media is on the record. actor james franco seems to be learning that the hardware, after he made overtures to an underaged fan. >> james franco got hot and heavy with a group of underaged girls. >> i just fell in love with you. >> but this week, life seems to be imitating art. >> i guess i'm just a model of, you know, how social media is tricky, you know? it's a way people meet each other today, what i learned, you don't know who's on the other end. i used bad judgment and i learned my lesson. >> so the question tonight, is franco having more fun, a hoax perhaps, or did the 45-year-old really try to hook up with a 17-year-old girl on instagram. it all happened tuesday night

after he was signing autographed of his broadway show "of mice and men." he asked a scottish lass to tag him. she did and he got in touch, asking how long will you be in new york? she replied a few days. it's my 18th birthday present. >> you're 18, he asked? whoer you with? do you have a bf? that's when things get even weirder. her answer, i'm nearly 18. my mom and not if you're around. >> franco wanted more, asking for her number. but this clever girl needed proof. it all sounded, quote, dodgy. franco obliged texting her not one, but two selfies. one with her name written on a piece of paper and yes, you're more. you're single, he asked? what's the hotel? should i rent a room? still skeptical, the teen replies, i'm come back when i'm 18. >> if it's a hoax, the purpose is to promote his movie coming out the same day as the trailer

was released that deals with the same subject matter, an older guy inappropriately dating a much younger woman. >> that's right, in franco's new movie "palo alto" he plays an older soccer coach that gets involved with one of his 14-year-old players. >> this isn't the first time we've seen possible hoaxes used to promote a movie, but it's the first time that an actor has done something allegedly so sleazy in the name of a hoax. >> franco, a self-promoting hoaxster? method actor? or a guy who made a strangely well timed mistake? we'll let you be the judge. for "nightline," lindsay janice, new york. >> i'm not sure i'm buying this. but the age of consent in new york is 17. thanks for watching abc news. tune into good morning america tomorrow. and as always, we're online at abc.com. good night.