Transcript for What happened when a gunman opened fire at Texas church killing 26, including children
A little church, quiet street, a small Texas town. Suddenly thrust into the glare of the national spotlight. It's heartbreaking. That church is my family. After a gunman opened fire killing 26 people during their Sunday ritual at a house of worship. And there's so many that are gone. It hurts so much. Sutherland springs joining Las Vegas, Orlando, Newtown, a list of names synonymous with mass shootings in what seems like an endless and accelerating stream of gun violence. And tonight new information about the killer, the military confirming he was convicted of domestic violence during his time in the air force. That record should have stopped him from being able to buy the murder weapon in first place. The assault began shortly after 11:20 A.M. In the midst of the morning worship service. The attacker, identified by authorities as 26-year-old Devin Kelley, parked his car at this gas station, then walked across the street to the first Baptist church. He was shooting people while he was walking in there. Reporter: Rosa Salis just got home in the hospital still recovering from a bullet wound in the shoulder. Everybody was so quiet. You could only hear the sound of the bullets and people screaming. People screaming and people crying. And mama, where are you? Mama! The little kids. Was anybody trying to get away? Was there anywhere to go? Uh-uh. There was nowhere to go. You were all trapped? We were trapped inside. She says as Kelley unloaded hundreds of roads reloading, he yelled this message to his victims. Is everybody done . That's how he said. I had my ears covered up. And oh, my gosh. You're like this and you're covering your head, what are you thinking? I shouldn't have gone to church that day. He told me not to go. Let's not go. Let's just wait till next week. I'm never going to see my grandchildren again, and I'm going to die. As he exited the church a local resident grabbed his rifle and engaged that suspect. I'm no hero. I am not. I just wish I could have gotten there faster. Steven Williford, his granddaughter ran him saying she heard gunfire at the church. Every time I heard a shock, I knew that probably represented a life. I was scared to death. But the former NRA instructor didn't freeze. He grabbed his gun, raced outside. He wasn't even wearing shoes. People at service, and their family. He spotted Johnny langendorff. The gentleman with the rifle came to my truck, he briefed me quickly on what had just happened and said we had to get him. That's what I did. We hit about 95 going down 539 to catch this guy. He just hurt so many people. My god, my lord protected me and gave me the skills to do what needed to be done. During the chase, police say the shooter called his father. The suspect used his cell phone to notify his father that he had been shot and didn't think he was going to make it. The gunman lost control of his vehicle and crashed it into a ditch about ten miles away at the Wilson Guadalupe county line. An autopsy confirms that Williford did shoot him but ultimately klley shot himself. Two gunshot wounds were from the armed citizen, one in the leg and the torso. Back at the church, another neighbor, David cassillas returned@ weeping as he turned his camera on. There's people dead in there already. There's one dead out here. Police suspect that the killing spree was rooted in a domestic dispute. Kelley hunting for his mother-in-law. The suspects a mother-in-law attended this church. We know that she had received threatening texts from him. Tonight a senior law enforcement official who viewed the video from inside the massacre tells ABC news there's little doubt the gunman came to the church to kill everyone in that building, period. Sounds like in this case the individual, who carried out the attack was going through a life of anger and disconnection finally focused on his in-laws as the root of his problems. Authorities say the 26-year-old, a former airman, was discharged in 2014 after serving a one-year sentence for assaulting his first wife and his 11-month-old stepson. Military records show he intentionally broke the child's clavicle and severely injured his skull. In reality the domestic abuse charges should have prevented anyone from obtaining guns, but the air force allegedly failed to enter information about Kelley's conviction into an FBI database. One source calling it an error. He applied for a legal permit to carry a gun in the state of Texas and was denied that permit. But at some point in 2016 and again in 2017 he did buy two weapons from academy sports, a chain store at two different locations in San Antonio. Academy sports confirmed the purchases in a statement adding both sales were approved by the national instant criminal background check system. We're cooperating with law enforcement as they investigate further. Kelley apparently had an affection for his firearms, posting a picture of his assault rifle on his Facebook page and could be heard shooting where he lived, a rural area north of San Antonio. The only thing unusual about them across the street is we hear a lot of gunfire and a lot of times at night. The gun used was a Ruger ar-556. The same type of weapon used in Newtown and Las Vegas, a weapon that was once illegal. We've seen so many mass shootings. What we've seen over and over again is that the assault-style rifle is the preferred weapon of killing. President Clinton signed into law a ban of new semiautomatic assault weapons and large capacity magazines. The law was in place for ten years but expired in 2004. What has happened is it becomes bigger than an issue just around gun ownership. It's can a proxy for the social battles and the cultural battles that seem to animate everything in politics right now. President trump was quick to respond from Jan. A very deranged individual. But suggest it was too soon to discuss gun policy. This isn't a guns situation. I mean, we could go into it, but it's a little bit soon to go into it. A similar sparesponse to what he gave in the wake of the massacre last month that killed 58. But in stark contrast to his stance in the truck rampage in New York City when he called for immediate changes in immigration policy. This is a mental health problem at the highest level. But critics point out that just weeks after his inauguration, trump signedh a measure rolling back regulation that made it harder for some people with mental illness to purchase guns. Critics of that regulation said the rule, which affected about 75,000 people violated the second amendment. Not everyone with a mental health issue is going to commit a mass casualty attack. But anyone who commits mass murder clearly has a mental health issue. Today on capitol hill -- It's hard to envision a foolproof way to prevent individual outrages by evil people. And Ted Cruz, a Republican senator from Texas, in a testy exchange with reporters. Are you thinking gun control now, sir? It is an unfortunate thing that the immediate place the media goes after any tragedy, after any murder is politicizing it. I think you've seen Republicans answer these events with predictable regularity. Almost like the tweets are cued up from the last time to talk about thoughts and prayers and the needs of the victims and hope that the nation can heal. What we're seeing with each of the passing events is Democrats are newly emboldened to call out their colleagues on the other side. It's no coincidence that these shootings have one thing in common, a weapon that is banned in most countries. Tonight the community remembering 26 lives lost. The dead and wounded ranging from just 18 months old to 77 years old. At least a dozen, maybe more, were children. That includes pastor frank pomero's youngest daughter Anna belle. They were out of town when the shooting happened but 14-year-old belle was in the church Sunday morning as usual. One thing that gives me a sliver of encouragement was the fact that belle was surrounded yesterday by her church family that she loved fiercely. For the Holcomb family death spanned three generation. Brian holcome was a guest speaker. The gunman burst in. He died along with his wife Carla, son mark Daniel and 1-year-old granddaughter, Noah. Crystal did not. Three more of her children also died. Eight members of a single family gone killed in the place that so many Americans feel safest -- their church. So many others fighting to survive tonight. For Sutherland springs, the focus is on the long road towards healing. For so many families here, faith will keep this community strong. Whatever life brings to you, lean on the lord rather than your own understanding. I don't understand. I know my god does. And that's where I'll be. For "Nightline, Matt Gutman, Sutherland springs, Texas. Our thanks to Matt Gutman. Tonight our thoughts the are with all who were touched by the senseless bloodshed.
This transcript has been automatically generated and may not be 100% accurate.