Transcript for 13-year-old survivor of Mexican ambush that killed 9 describes harrowing ordeal
There's five kids signature on the side of the road got shot on the mouth, shot on the foot, shot on the leg. They just started hitting the car first with a bunch, a bunch of bullets. Reporter: These are the horrifying sights and sounds. The bodies are burnt inside the vehicles. Reporter: Of a brutal massacre that shocked the nation. This is for the record. Nita and four of my grandchildren are burnt and shot up. Reporter: Three American women and six children murdered. Allegedly gunned down by members of a drug cartel. Some of the survivors seen here all members of the same fundamentalist Mormon community, alive in part because of this brave 13-year-old boy, hailed a hero after walking 14 miles to get his wounded family members help. Now nearly a week after the incident Devon Langford is speaking out alongside his Going through my mind was to get help because every one of them were bleeding really bad. So I was trying to get in a rush to get there. Reporter: He and his extended family, 17 in all, were traveling in three separate vehicles in a remote mountainous area south of the U.S. Border. According to reports, Mexican officials suspect cartel hitmen are behind the attack. They were big guns and they were -- they were in masks. I was trying to duck down, and my mom got everybody down. It felt real scary and it felt like a lot of bullets. Reporter: Devin along with his brothers and sisters were in one of the vehicles. His mother, dawn, had desperately tried to get them to safety. Car didn't work. So she was just trying to start the car as much as she could but I'm pretty sure they shot something so the car wouldn't even start. Reporter: One of the last things he remembers her saying -- To get down right now. She was trying to pray to the Reporter: Donna and two of her children, 11-year-old Trevor and 3-year-old Rogan, were killed. But Devin was able to save the rest of his siblings. Afterward they got us out of the car and they just got us on the floor and then they drove off. I walked a little while. I couldn't carry them no more. So I put them in the bush and I wasn't hit or nothing. So I started walking. Reporter: He set out in search of help. Still afraid his life was in danger. Walking all those miles was if there wasn't anybody else out there trying to shoot me or following me. I was trying to hide myself the best I could under a bush. I prayed a lot. Afterwards I got back up and started walking and prayed for a safe journey and that they're still alive and that they can make it. Reporter: After a 14-mile walk this audio message sent to a family group chat captures the moment Devin reaches members of his family. We have Devin. He ran all the way home and he says that the rest of the kids that are still alive are up under a tree. And then we were taking them to a hospital so, I was so glad. My boy's a hero simply because he gave his life for his brothers and sisters. Reporter: Authorities say more than 200 rounds were fired. Devin's mother Donna ray Langford as well as rannia Miller and cristia Langford Johnson were killed along with six children including two of Devin's younger brothers. The whole thing was a bloody massacre is what it was. On innocent lives. The most innocent. Reporter: Eight children survived. Some were taken via helicopter to a hospital in Mexico and later across the border into Arizona by ambulance. Christina's baby is alive. Praise god. We got faith. She is alive. Do you understand me? God is so good, you don't even know. Reporter: Christina Langford Johnson's 7-month-old was among those who lived. Baby faith is her name. She actually miraculously survived. And after hours and hours of being alone by herself in the car they were able to find her. Reporter: Leon Lebaron, one of Christina's relatives, showed us this video of when baby faith was found. I walked around the vehicle and opened the door and there was a car seat and there was a bullet hole through the canopy on the car seat. And we opened the canopy and the baby was smiling at us. Reporter: The families, who have dual citizenship in both the U.S. And Mexico, have lived in this border region for decades, before the cartels moved in. And when I first moved there, our little farm, there was a paradise, for children, for families. And we lived really safe. And had a good life. I have fond memories, really fond memories of my childhood there. Reporter: One of the reasons why the drug cartels are so prevalent in this area is because it's incredibly remote. You can see behind me it's all mountains and there aren't too many police officers sort of guard this area. And that's why the cartels feel they can run rampant here and do whatever they want. Mormons have a long history in Mexico. Christina Rosetti studies the religion. So starting in the 1890s mormons began moving to Mexico to be able to practice plural marriage and polygamy. Reporter: Not all the mormons here practice polygamy and those that do are not associated with the lds church in the U.S. Now David says he's left with no choice but to leave. Not only have I lost a wife and two children but having to move the rest of my family with really no place to go at this point. Reporter: Last Thursday David, Devin, and the rest of their extended family gathered to lay some of their loved ones to rest. The toughest part for me was saying good-bye. Yeah. It definitely was. Saying good-bye to two innocent lives that were cut short and a vibrant wife that lived life to its fullest, that had many friends and was loved by all. By everybody. Reporter: Last week president trump tweeted "If Mexico needs or requests help in cleaning out these monsters, the united States stands ready, willing, and able to get involved and could the job quickly and effectively. At the time Mexico's president said they would handle this alone. But now Mexico asking for the FBI's help. And earlier today Mexico's public security minister announcing they've detained individuals possibly connected with this attack. As the investigation continues, Devin wants the world to remember the family he lost including his mother and two little brothers. She was a nice person and a brave woman that tried to save her kids. Trevor was just a happy little -- happy kid. We did a lot of things together. Rogan, he was just a happy little boy. Reporter: And despite the tragedy David says their faith is what's holding them all together. My boy, Donna's son, was questioning why god would allow something like this to happen. I told him that instead of looking at the three we've lost look at the seven that are allowed to stay with us. All seven of them if you look at every one of them individually, every one of them were a miracle to be alive. Our thanks to Tom. The FBI is also responding to an invitation by the Mexican government to participate in the investigation, saying they "Remain committed to working alongside their international partners to help bring justice to the perpetrators of this heinous act of violence."
This transcript has been automatically generated and may not be 100% accurate.