this is "nightline." >> tonight, isis in america. opducing young pele, like this north carolina teenager, from >> isis soldiers, who would wear their socks above their ankles. heed doing thatf.rt sta >> targeting the isolated. manipulating their emotions. >> these videosre a inspirational. >> a year-long diane sawyer investigation. the tools of rtha out for.ec trt plus, mural, mural on the wall. is this the largest of them all? >> how many brushes did you use? >> sometimes a broom. >> a broom? >> a broom. stars, like kate hudson and howie mandel, now striving to break a world record. >> so many things cano g up here.

so i have to be very, very focused and very, very sharp. >> his 60,000 square foot tribute to los angeles with a powerful message. but first the "nightline 5." >> okay. i never thought i'd say this. but i found bladder leak underwear that's actually pretty. surprised? it's called always discreet boutique. it looks and fits like my underwear. i know what you're thinking. how can something this pretty protect? hidden s a super soush ant core that quickly turns liquid to gel for incredible protection. so i feel protected and pretty. >> new always discreet boutique.

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this week new york was once again hit by terror, the most deadly attack here since 9/11. tonight we explore a terrifying reality, that some of the most dangerous threats to our country couldm within. abc's diane sawyer investigates isis recruiting tactics, revealing their shocking reach american households,to turning impressionable young people into deadly weapons. >> reporter: this week in america -- >> there's been a violent -- >> reporter: a 29-year-old man who emigratedago takes a truck and mows down more than 20 people on a bike lane. on his phone, 90 isis propaganda videos. it seems for years now we have been talking about men like these, terror, radical jihad. but tonight in this report we are tracking something ng to learnyi how r re iacshingsi into all kinds of american homes. muslim, nonmuslim, urban, rural. there are 1,000 terror

investigations under way, reaching across of the union. and 40% of those charged in supporting isis terrorism did not gw which brings us to the young man who lived here in rural north carolina. >> police! >> what is your emergency? >> a desperate father called 911 about his soneliourus bni statues in their house. >> i need somebody as quick as possible. >> we have units en routethe t what -- >> this is your son? >> yes. >> reporter: you can hear that son in the background. >> they're going to throw me in jail my whole life and kill me. why are you trying to say i'm >>eporr: a a terrorist? justin sullivan grew up as a boy in a catholic home with trophies, friends, a bedroom filled with childhood toys. his dad a retired marine captain rich sullivan. >> i imagined him joining the military.

and following my footsteps. >> reporter: but his high school reported to the parents justin had violent fantasies in his writing and suspended him. they said he needed serious help. the parents sent himo a tpsychologist but admit they downplayed what they were hearing. as justin continued to isolate himself on his computer, obsessed with violent video games. and images of isis. >> isis soldiers. who would wear their socks above their ankles. he started r dortengoir: the pa idea that their 18-year-old son, alone with his computer, had reached out to isis recruiters. he sent a message. in less than 24 hours, a top captain of isis responded. isis recruiters seemed to know exactly what to say to weaponize someone like justin. there is even a captured terrorism recruiting manual. in phrases from other isis case. target is alienated like

justin, start with encouragement and praise. like, welcome, brother. blessings upon you. we know justin loves the video game "call of duty." isis has an idea, "call of gee jihad." recruiters tell justin there's something he can do to be a real one night in december 2014 in what seems to be a practice run, justin puts on a ski mask and murders a neighbor with his father's rifle which he hides. police find the neighbor's body but have no suspect. then in a few months he tells his isis recruiter he's ready to go big. and isis says, make a videotape so they can be sure he's fame miss. famous.ng tget an assault rifle. and slaughter people at c carol, but as the clock is ticking down his parents discover a package

containing a gun silencer. >> i called the police department, i need to talk to somebody in homeland security. >> reporter: captain sullivan discovers the fbi was already secretly tracking his son because of that first call to 911. agents descend on the house, arresting justin. he pleads guilty to terrorism and to the neighbor's mu.errd hi justin is clearly mentally ill. >> he could very well be on the brink of schizophrenia. >> reporter: he has never talked about why he was trying to become a soldier of is.is prepa collect call from -- >> justin sullivan. >> -- an inmate at the county detention center. >> reporter: he knows we've been asking the question. like a isis gave him a place ts brotherhood. >> reporter: his fantasies of heroism from the violent video games have become reality. >> it was like revenge. and you wanted to be like

acknowledged by the islamic state. you want to be looked at as a he remembered. >> reporter: at one point he claims he wouldn't really have gone through with a mass attack but we wondered does that mean he's sorry for what he did? >> why should i apologize? i got two life sentences. who'ser than me? >> reporter: mary mac cord, former head of the federal office that has prosecuted all 147 isis cases in the u.s. in the last two and a half years. including the case of justin sullivan. >> i don't think justin sullivan cared anything about the religion. he thought that this was essentially a death cult. >> reporter: mccord says it might surprise you how many of the cases her office has prosecuted have little to do with twisted religious beliefs, more to do with young men and 89% are male, just feeling powerless. for your teenagers it's just a few clicks away and most parents don't know.

>> they have an entire chat room to give you information how to protect your computer from surveillance and the fbi. >> reporter: seamus hughes of george washington university leads a program and group that tracks and analyzes extremists online. >> they just posted this? >> they just posted this fiveag >> reporter: if you think smart, successful kids are somehow immune to the trap doors online, come with us to the federal transfer center in oklahoma city. there is someone who can answer questions about the story of two honors students from small mississippi towns. one of them a cheerleader, the other a soccer player. through the door, mohammad daklala, a young man who once had a bright future. had you ever been arrested before? >> no, ma'am. never before. >> nothing? >> no, ma'am. i mean, unless you count like car tickets. >> one of your friends was quoted saying, he's the guy who was never in a bad mood. >> that is true. yeah.

>> reporter: he is the son of a muslim father and a catholic mother who converted. he was a straight-a student in graduate school, studying psychology, when he met his first real girlfrndie. a superstar who grew up going to church on sundays. her dad a police officer, her mother a school principal. >> super intelligent. always very polite. >> jalen delshon young. >> she was so smart, top of her class, studying to an doctor. >> reporter:ly admits she was his first real relationship. what was it about her? >> well -- looks, one thing. and the next thing to look at is intelligence, really. >> reporter: so what happened? jalen young has admitted in court that she was the one who became so overwhelmed with her premed studies, that anxiety and depression took hold. so she began to search for

spiritual solace and looked at idealistic propaganda videos for isis. >> these videos are dangerously inspirational. if you're in a state of anger or state of depression, they really want to try to hook you in. >> reporter: but it was jalen herself who says she was the firs o drawn toli islam. she like the strict rules of behavior. she says she became convinced by isis was misrepresented in the media. in a surprise, the smiling former cheerleader began wearing an hikab. she tells her boyfriend she wants him to watch propaganda videos and come with her to live in syria. he says, in truth, he just wanted to be with her. are you saying you did this for love? >> like blind love. >> but theyou y're a savage organizati >> we took that to be like more of a biasedhe media.

>> did you really believethat? avok at your 4.0 ste.raeright, to be honest with. >> you were willing to kill americans? >> no it was more just -- leek, you kn, i'll want to help as much as i can. >> reporter: he told me he hoped maybe he could work in the pr department. then ne oago, after months of planning, these two college students packed their bags and headed to the regional airport to travel to the middle east. what do they bring with them? craft supplies, a scrapbook, a bar of soap, a pack of starburst minis, and his nintendo. but it turns out their isis friends online were in fact undercover agents for the fbi, who moved in and arrested them. at sentencing, defense attorneyr gu tsehe fallen into

depression, confusion, gotten lost in the internet. but the prosecutors aredgu, what they were prepared to join up. both of them expressed deep remorse, but tonight jalen young is spending 12 years in prison after instigated the idea. we asked to talk to her, she declined. mohammad daklala is now in for for eight years. if you have a machine 24/7 whoso whole purpose is to recruit any child isil any religion? >> anyone is vulnerable. >> the idea that you would go to joinomeone who engages in beheadings? that you would suspend critical thinking about that? >>he vile and disgusting things that they see, because somehow it all fits into the narrative. >> reporter: tonight, a father from north carolina has a

warning for parents. remember, he is a marine who fought the enemy abroad. >> here i am defending our country against domestic enemies. which so happen to be my son. i didn't think it was this close to home. >> reporter: a father awash in regret. >> i think we failed. >> our thanks to diane sawyer and her team for that compelling report. up next, he's used to painting stars. now he's painting a building. how this l.a. street artist is on his way to a guinness world record. ♪ ♪ ♪

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he's determined to break the guinness world record for the largest mural painted by a single artist. street artist robert vargas is using a 60,000 square foot side of a building as his canvas. why? here's abc's elizabeth vargas. >> so many things can go wrong up here. so i have to be very, very focused and very, very sharp. >> reporter: at the corner of fifth and hill streets in downtown los angeles, something unprecedented is happening. suspended high on a scaffold with his cans of paint and an array of brushes, a single artist is trying to do something no one has ever done before. >> we want for it to be the biggest record. >> reporter: robert vargas. no relation. he's been working every day to have three months painting the largest mural in the world by a single artist. >> i'm going through tons of brushes. >> reporter: each morning on his

way to try and set the guinness world record, he greets the denizens of this gritty block. many of whom have spent weeks watching him work painting the 60,000 square foot creation he calls angeles. >> how big a brush do you use? >> sometimes a broom. >> a broom? >> a broom. >> reporter: he has spent hundreds of hours alone on his scaffold with his brooms and brushes. a far cry from his usual high-energy performance painting. >> everyone, give it up for annabel! >> reporter: vargas became famous for edgy portraits, part street art, part high art, part mystical experience. you can find him painting on his canvas on the ground in cities across the world. communing with stars like kate hudson, william macy, howie mandel. as well as residents of skid row. all of whom happily sit for the vargas experience. it usually happens with a crowd

leaning in. the spectacle of vargas at work as riveting as the painting he creates. music playing loud. no talking ever allowed. and it's all over in minutes. one man's glimpse into another man's soul, he says. all rendered in chalk and acrylic and water. >> it's a very intense sort of dance. >> i use a variety of different mixeda. charcoal to ink and enamel paint, oil bar sticks, water, brushes, tease things. >> i saw you pour water on one. and i nearly grabbed your hand to say, you're making a mistake, you don't mean to do that. >> reporter: his talent of portraits vargas said grew out of a need to prove himself as a young artist. >> when i was in the fourth grade, lost a drawing contest because the judges thought that i had an uncle that lived at home and did it for me. >> really? >> it was that experience that

also was a little bit of a birth of me painting live. >> reporter: while his portraits can take just six minutes, the mural will take six months. the biggest challenge, painting a scene he can't see because he's so close. >> on a 14-story building, when you're a foot and a half away from the wall, no use of grids, no use of prodirections, no use of stencils, all freehand with a brush. it's very challenging. >> for the nonartists in the audience, explain what that is. >> typically if you're using -- if you're painting on a really large scale, you'd like to grit it out the way the old masters did. >> what did michael an gel although do at the sistine chapel this. >> grit it out. he made his initial drawings and studies and created grids to map it on the ceiling. >> why do you do it freehand? >> i trust my intuition. >> reporter: the mural is an homage to the people of los angeles. what's the message behind the mural? >> unity. hope. especially right now with the

current climate of what's going on in the world. the anchor for the wall is a tungava indian girl, they're the original people that inhabited the l.a. basin. >> reporter: a salute at a time race relations are tenuous and tested. >> the placement of this wall is one that will reach two different counterpoints with the social and economic classes of los angeles. my inspirations and my friends are coming in all different shapes, sizes and colors. and i want to celebrate that. >> reporter: the project is in the shadows of the glittering new high rises and just above the nation's largest homeless population. >> it's a wall that's meant to reach everybody. and connect with people. show that the homeless people are also important and significant. >> why do you do that? >> because they're part of my community. i don't see any separation between where they are and where i am. >> reporter: for "nightline," i'm elizabeth vargas in downtown

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finally tonight, houston strong. the city held their world series victory parade today for their beloved astros. marching bands, confetti, and fire trucks rolling through the streets. but the highlight of the day was the champs themselves, of course. congratulations, houston, from all of us, even dodger fans. thanks for watching abc news. as always we're online at abcnews.com and our "nightline" facebook page. good n