Transcript for Parents of boy killed on Kansas water slide recall horrific day
A tragic story, we're hearing from the parents of the boy killed on that extreme water slide billed as the world's largest. Their emotional and candid account of the unimaginable. Matt Gutman sat down with the family who has a message for us all. Reporter: On the August day the schwabs went to the world's tallest water slide, admission was free for the families of state legislators. But that thrill ride would cost the Kansas state let gislator and his wife most dear. Six went to the park and five came back. Reporter: For the first time Scott and Michelle Schwab recount that tortured Sunday. Hoping that sharing their story will help keep Caleb's memory alive. I still remember him sitting on the floor, we're going to go to the park! He lit up, so excited. Reporter: The schwabs piled their four boys, including 10-year-old Caleb, into the car. They had a nickname for their second son. Called him monkey bear because he climbed everything. He would hug like a bear. He's 10 years old, he still wraps his arms and legs around you for a hug. Reporter: He was that kind of brother. You see him here dancing with his baby brother Isaac. When they got to the park, Caleb and his 12-year-old brother Nathan went right to the 170-foot scaffold of verruct, which means "Insane" in German, billed as an extreme thrill ride. I said, brothers stick together. He says, I know, dad. Reporter: It was the last time his parents would see Caleb alive. Big brother Nathan was dutifully waiting for him at the bottom when the unimaginable happened. He was screaming. He flew from verrukt. Reporter: Nathan ran to find his mother but the horror made it nearly impossible for the 12-year-old to explain. There was a gentleman who wouldn't allow me to come close enough to see what was going on. He just kept saying, "No, trust me, you don't want to go any further." Reporter: Scott was in such shock, good samaritans had to confirm the incomprehensible. I need to hear you say it, is my son dead? He said, yes, your son is dead. Put us on a golf cart, sorry you lost your son. It was surreal. I hardly remember driving home. Reporter: So far no criminal charges have been filed, but the family has settled with the theme park for an undisclosed sum which will go to Caleb's three brothers. The family is still pursuing legal action against others including the firm contracted to build the slide. They declined our request for comment. They call it an accident. But I think you and your attorneys believe that negligence caused this accident. Yeah, yeah, it's an accident but there's an accounting because someone was negligent. Reporter: In a statement to ABC news, the park said it was heartbroken over the tragedy and the safety of our staff and our guests is our top priority. The park's verrukt water slide set to be torn down. This is the view from the top of verrukt. Thrill-seekers fall 17 stories in seconds, hitting speeds of nearly 70 miles an hour. Commercials for the ride even asking -- Are you insane? When the ride first opened three years ago, many were asking a different question. Is it safe? Concerns only heightened after this video from the ride's testing phase appeared on the travel channel show "Extreme water parks." Sandbag dumb he's launching off the slide. The ride's opening was repeatedly delayed while designers attempted to work out the kinks, adding in more safety features like netting and safety belts. When it opened it was finally deemed a feat of engineering. I was the first TV journalist to go down. Literally not for the faint of heart. Reporter: Lifeguards, safety checks, and on this day at least, a park employee at the top of the ride reading a two-page liability agreement. There's a risk inherent to the activity -- Reporter: My first trip down was a vertigo-inducing plummet, but overall fun. A completely different scene than the tragedy that unfolded when Caleb Schwab lost his life. But it's easy to see how in a fast-paced ride like this, things can go wrong in an instant. This man was in an Austin, Texas, slide when he ka reared off the edge, falling down a rocky cliff. He suffered a broken arm and fractured ribs but survived. In this video a man desperately holds on to another rider. After falling off of the raft before eventually being plucked back to safety. I've got three kids that tale from the ferris wheel. Reporter: Last August three girls were injured when they fell off the ferris wheel in green county fair, Tennessee. Last April in Texas a teen died at a church carnival. She was hurled from her seat on a small spinning ride like this one. There nor federal regulations governing amusement parks and the enforcement of state laws is patchwork. The schwabs and their lawyers are trying to change that. They're still pursuing but sustaining themselves on faith and friends. ??? Reporter: At Caleb's funeral his baseball team huddling with Scott. And it was Scott's friends who a few months after that funeral took him on a retreat and forced him to spend time grappling with his grief. After Caleb was killed, you penned a letter to him. They gave me a notebook, pen. Said, hang out by the river and write a letter to your son, then you need to write the response. So my heart had to say what I never really got the chance to say. It was hard. But it was a release. Reporter: Caleb's brothers keep going by keeping their brother in their minds. Watching those videos. Some of them how-to movies he shot himself. So in order to push that button in, we need Toake this thing out. And that's kind of the key hole. Reporter: And that one of him cradling his little brother. There's times, I can't look at that now. Then there's other times you can't sleep, you want to look at it. What do you miss most about Caleb? Giving him hugs. Hugs. Hearing about his day. My morning hug. Watching him play soccer. Why was it important for you to do this interview? We have a box of greeting cards from around the world. We just want people to know we're thankful. Yeah, we're still hurting, but we're going to be okay. Reporter: For "Nightline" I'm Matt Gutman in Kansas City.
This transcript has been automatically generated and may not be 100% accurate.