tonight on "nightline" -- a shocking end. after their mom disappeared and their dad became a suspect, the lives of two little boys are taken by their own father in a fiery murder/suicide. tonight, the chilling message in their final moments. and what really happened to the powell family. apocalypse now? if so, these doomsday preppers are ready. how and why they're gearing up for the end of the world. stockpiling everything from ak-47s to honeybees. and slackliners. the move that upstaged madonna's halftime performance put the sport of slacklining front and center. tonight, we'll show you why many have tried but only one was chosen. the super bowl's own sketchy andy shows us the skills.

>> from the global resources of abc news. with terry moran, cynthia mcfadden, and bill weir in new york city. this is "nightline." february 6th, 2012. good evening, i'm bill weir. we begin tonight with an explosion of fire that suddenly ended three lives at the center of an unusually volatile and public family drama. the victims were two little boys. the suicidal perpetrator was their father. a man suspected but never charged in the disappearance of his wife two years ago. the boys' grandparents said they feared that father might be capable of violence. tonight, they have their terrible confirmation. here's abc's neal karlinsky. >> reporter: it was a twisted murder/suicide. two young boys killed at the hands of their father josh powell in a terrifying end to a long and sordid nightmare. >> i was afraid that if he had the chance, the only way he

could win this game that he was playing was to kill them. >> reporter: but what happened inside the house before the flames broke out is far more sinister than anyone could have imagined. police say josh powell tried to kill his 7-year-old son charles and 5-year-old braden with a hatchet before the fire could take their lives. >> i don't know if his intent was to try to put them out before the fire got them but he didn't do a very good job of it. >> reporter: josh powell was no stranger to police scrutiny. he was the prime suspect in the disappearance of his wife, susan powell, missing over two years now. just before 12:30 sunday afternoon, the two boys were escorted to josh powell's home by a caseworker for a court-ordered visitation with their father. police say they locked the caseworker out and ignited two five gallon cans of gasoline, sparking an explosive fireball that leveled the house, killing both boys and powell. and they say there were signs he had been carefully planning his final act. he donated their toys to a local

charity over the weekend. and sent good-bye e-mails to several people. >> we've discovered multiple e-mail also he sent to his pastor, he sent to his cousins and he sent to other people that are a bit longer in length. they dictate what to do with the utilities. what to do with his money. what to do with certain aspects of his life. >> reporter: he said nothing about his missing wife. powell's story to police was that the last time he saw susan was at their home in utah just before taking the boys on a midnight camping trip. a story that never quite added up. >> he's disturbed. he just -- disturbed. the act that he did was cowardly. >> reporter: today, susan powell's parents, chuck and judy cox, say their grandsons had recently started remembering more about what happened on that night in 2009. when their mother vanished. and were beginning to see things about the camping trip. they say one of the boys even drew a picture indicating their mother was in the trunk of the car. >> that's daddy. that's charlie and that's me. and then he said, well, mommy's in the trunk.

>> reporter: shortly after susan powell vanished, josh powell moved to a town south of seattle with their boys and had been living with them there at his father's home. both sat for an interview with abc's abbie boudreau in 2011. >> everyone who knows me knows i would never hurt her. i would never hurt my boys. >> reporter: late last summer when the home josh shared with his father was raided by police, josh lost custody of two his boys to susan's parents. in the raid, steven powell was charged with possession of child pornography. >> susan was very, very sexual with me. she was very flirtatious. i mean, i'm her father-in-law and i did -- i mean, we interacted in a lot of sexual ways because susan enjoys doing that. >> you knew about this. >> she's a very flirtatious person. >> reporter: susan's friends say she never wanted her children anywhere near her father-in-law. >> the very first time i met josh and susan, they told us

about his dad and how he was into pornography and we knew he was a pretty bad guy and susan had basically told us, "he's never setting foot in my house." >> in fact, susan's sister told me when they would come to visit, susan would stay in a different home with the two little boys while josh powell stayed with his father. why? because the father-in-law was so creepy. >> reporter: court-ordered supervised visits began in november of last year. josh powell was fighting for their return ever since. in a court filing this past wednesday, he made a strong appeal. i've proven myself as a fit and loving father who provides a stable home even in the face of great adversity. a lesser person would fall under the intense scrutiny i am facing. but the judge requested a lie detector test and further evaluation. >> i don't think the order of the evaluation caused this. i think this has been coming, it's been brewing for a long, long time.

and even though the family begged the court for help, those visitations were in place and they were allowed. >> reporter: the boys' grandparents say they're convinced josh powell saw the kids as his own, like possessions, and he didn't want anyone else to have them. >> her blood sister told me the parents begged for him not to have visitation at all. i mean, come on, what more do you want? the mom has been murdered. she was taken out of josh powell's home. and murdered. with the boys in the car. he also had them in a scenario with his father, who is now behind bars for child pornography. under these circumstances, the judge should not have ordered visitation at josh powell's home. >> -- got to bond very closely with them in the three months, so we'll just have to deal with memories. >> he could have at least left a note behind, saying where susan

was. >> reporter: tonight at the boys' elementary school, children are leaving messages trying to make sense of the loss of their schoolmates, a loss that no adult can fully explain. >> it just seems unreal. >> reporter: at the cox home, children's beds will sit empty. an entire family has been wiped out. i'm neal karlinsky for "nightline" in graham, washington. >> and "20/20" will delve deeper into the powell family tragedy this friday. an hour long special titled "sins of the father." thanks to neal karlinsky. just ahead, a new group of doomsday believers is gearing up for the end with ammo and honey. plus, how madonna made this guy and the art of slacklining the buzz of the nation.

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>> announcer: "nightline" continues from new york city with bill weir. people have been predicting the end of the world since the beginning. but this year, doomsday predictions seem to be urgent and widespread. whether you blame the mayan calendar or melting ice caps, tonight we meet a diverse collection of folks who aren't just sitting around waiting for the worst, they're getting ready to live through it. here's abc's david wright. >> reporter: volcanoes. earthquakes. financial meltdown. come what may, tim rolston is ready. >> freeze-dried food, survival gear, first aid, ammo. >> reporter: what do you think is going to happen? >> there's a lot of different things that could happen.

for me, i look at prepping kind of like insurance. you have car insurance, health insurance, life insurance. >> reporter: this is apocalypse insurance. >> this is life assurance. >> reporter: the scottsdale father of two calls himself a prepper. part of a growing movement preparing for the end of the world as we know it. >> in the beginning, my wife really wasn't on the same page as i was. but the more information i started to give to her, it opened her eyes to the other potential threats out there. >> reporter: he's turned the family's two car garage into a staging area. oh, my gosh. quite a man cave. >> it's really ready to go. >> reporter: you keep this packed at all times? >> all times. >> reporter: he has cartons of canned chicken with a shelf life of 15 years. ways to purify even the most polluted water. >> not bad? >> reporter: not bad. sugary. and weapons. lots of weapons. >> that's my son's actually. >> reporter: your son has an ak-47? >> of course. >> reporter: once a week, tim takes his sons out to the desert

about 30 miles away on a practice run. >> the bad guy is the red guy. >> reporter: a dress rehearsal for doomsday. >> go, go, go, go, get 'em. nice shot. >> reporter: eventually, he plans to build an underground shelter here, a converted shipping container, tricked out with everything they need to survive. >> you just never know. i have a lot of other religious friends that say i don't want to prepare, i'll just go to heaven. i go, well, do you know what it feels like to starve to death? >> reporter: he's one of several people the national geographic channel followed for their new series "doomsday preppers." there's a couple in texas who have converted school buses into getaway vehicles. >> go, go, go, go, go. >> reporter: they live off the grid, filter their own water, and store enough canned goods to last 22 people for years. and there's the new england mom who calls herself the doris day of doom. >> i'm preparing for a black

swan event like a catastrophic new madrid earthquake. >> reporter: cathy doesn't exactly fit the survivalist stereotype. she isn't stockpiling weapons. instead, she keeps bees. >> in a breakdown situation, those bees become not just food for us but they become honey that we can barter for. those bees are the essence of resilience for us. >> honey could become very valuable. it's one of the only foods that won't go bad. you can store it forever and ever and ever. >> reporter: paranoia is part of of the zeitgeist right now. so much so that last night during the super bowl -- ♪ looks like we made it >> reporter: -- general motors conjured up this vision of the day after tomorrow. where the only survivors of the apocalypse are these dudes. >> where's dave? >> dave didn't drive the longest-lasting, most dependable truck on the road.

>> twinkie? >> reporter: that hell in a hand basket motif seems to be everywhere. even on comedies like "parks and recreation." >> what can i do you for? >> the world is going to end tomorrow at dawn. >> aw, nuts. >> the entire planet. >> not giving me much notice, let me see what i can do. >> reporter: some fear our downfall will come from our dependence on technology and fossil fuels. forcing us back to the stone age, "mad max"-style. others are convinced the mayans had it right. that in 2012, just a few months from now, we'll simply run out of time. of course, there's always the ever popular christian end game, the rapture. enough people believe the end is nigh that prepping is now big business. a little over a year ago, we went to the middle of the mojave desert to meet robert, a real estate developer to end all real estate developers. he's converting a cold war

bunker into a luxury modern shelter. >> that's noah's ark, just happens to be underground. >> reporter: underground condos fortified against the unthinkable. complete with a hospital and movie theater. price tag $50,000 per unit, up front. long before this one was complete, it was almost sold out. he's also building another shelter in indiana big enough for 80 people. that one's further along. almost complete. also almost sold out. >> we're looking at doing 20 in china, three in taiwan, romania, russia, everywhere. people are coming at us from everywhere. >> reporter: paranoia sells. some of the doomsday preppers know it too. tim doesn't just stockpile this stuff, he sells it. you have a website? that people go to? >> yeah, we do. it's called "gear up center." people can go there, buy anything, order it online. >> reporter: prepared for anything and making a profit too. >> hi, boys. let go, we're going on vacation, come on. >> reporter: i'm david wright for "nightline" in scottsdale, arizona.

>> the new series "doomsday preppers" premieres tomorrow night on national geographic channel. didn't nostradamus warn about madonna and some sort of slackliner at a halftime show? he was right. we'll check them out when we come back. [ kyle ] my bad. [ roger ] tell me you have good insurance. yup, i've got... [ dennis ] ...allstate. really? i was afraid you'd have some cut-rate policy. [ kyle ] nope, i've got... [ dennis ] ...the allstate value plan. it's their most affordable car insurance -- and you still get an allstate agent. i too have... [ dennis ] ...allstate. [ roger ] same agent and everything. [ kyle ] it's like we're connected. no we're not. yeah, we are. no...we're not. ♪ the allstate value plan. dollar for dollar, nobody protects you like allstate.

so, if you watched the super bowl, well, you helped make it the most watched television broadcast ever. actually peaked at halftime when an estimated 114 million saw madonna get momentarily upstaged

by a guy with a not so tight rope and apparent lack of feeling down in his vince lombardis. here's abc's matt gutman with tonight's "sign of the times." ♪ there's nothing to it >> reporter: you knew there'd be a breakout star in madonna's roman-themed halftime extravaganza on nbc. maybe it would be the god mercury with those nifty wing sneaks and that harp. maybe the acrobatic hard core four. ♪ m.i.a.? nope. it was andy lewis. anointed with the peck from the queen of pop. bouncing right into your living rooms. in a modified tunic. a perfectly choreographed 28-second performance that seemed two parts wow and one part ow. that's not exactly a tight rope. it's called a slackline.

a one-inch thick ribbon of nylon which is kept, well, slack. giving folks like sketchy, andy lewis says he's known in this world, their fledgling sport, not so incidentally called slacklining. >> i would say that the super bowl is definitely the most public place that i've ever slacklined. >> reporter: we caught up with the california-born, carrot-topped acrobat this morning. >> when you have that many people live, there's this energy that kind of gets put into you that you can't access any other way and it's amazing. the music, the flashes, the lights, the moment. it's just a very spectacular thing. >> reporter: known as mr. slackline on youtube, lewis is the extreme sport's only star. in fact, it's so new it doesn't have any major sponsors. founded in the early '80s in colorado, it spread, becoming popular on the beaches of california. originally about walking the line. it's now a competitive sport focusing on tricks.

one of the reasons it's also called "tricklining." all this sketchiness, slacklining in the nude, over roaring rivers, requires years of practice, extraordinary balance, and a brass set of -- andy "sketchy" lewis says you get used to it. >> just like any other extreme sport. you've got to take some pain and learn how to do the tricks. you sprain your ankle sometimes. you hurt your knee, you land on it wrong, doing a back flip, you slip and land on your back. >> reporter: but lewis stuck last night's flip, opening the door for the underground community's coming out party. it has already cornered a niche market on youtube but post-super bowl it's expanding the fan base from a few hundred thousand viewers to a cool billion. for "nightline," i'm matt gutman on terra firma in miami. >> i'm just picturing all those 13-year-old boys digging out the clothesline. be careful. thank you for watching abc news. seeck in with "gma" and we'll