Who is Devin Patrick Kelley, the gunman who officials say killed churchgoers in Sutherland Springs?

In the immediate wake of the mass shooting in Sutherland Springs, Texas, only a patchwork of fragmentary details was available about Devin Patrick Kelley, the 26-year-old identified by law enforcement as the gunman who opened fire at the town's First Baptist Church Sunday morning, killing more than two dozen people.

Neither the information available from public records nor officials investigating the crime offered an indication of what precipitated the deadly attack on the congregants.

Wilson County Sheriff Joe D. Tackitt Jr told CNN on Monday that Kelley's former in-laws attend the church occasionally, but weren't there when the shooting occurred, the Associated Press reported.

Kelley, a former US Air Force airman, had a string of legal troubles beginning at least in 2012. That year, he was court-martialed and sentenced to a year in military prison for assaulting his wife and child, Air Force spokeswoman Ann Stefanek told The Washington Post.

According to Stefanek, Kelley enlisted in 2010 and served as a logistical readiness airman at Holloman Air Force Base in New Mexico. Court records in nearby Alamogordo show that in October 2012, Tessa K. Kelley filed for divorce against Devin P. Kelley. The case appears to have concluded in a matter of days, with a settlement recorded the same day as the initial filing. There are no children listed in the proceedings.

Following his prison sentence, Kelley was reduced in rank and released from the military with a bad conduct discharge in 2014.

In August of the same year, he was charged with a misdemeanour count of mistreatment, neglect or cruelty to animals in El Paso County, Colorado, where he lived at one point, records show. The case was eventually dismissed, although the details and circumstances surrounding the charge weren't immediately clear.

Records indicate that Kelley lived for some period on a property valued at about $800,000 owned by his parents in New Braunfels, Texas, a rural suburb of San Antonio about 55km north of Sutherland Springs. The secluded home sits on 11ha of wooded farmland, separated from the nearest main road by a long private driveway.

A mourner holds a candle during a vigil held for the victims of the fatal shooting. Photo / AP

Neighbours told local media that Kelley lived in a barn in back of the home with his current wife and 2-year-old son. They said the family had lived there for more than a decade.

Dave Ivey, who identified himself as Kelley's uncle, apologised to the shooting victims in an interview with NBC News.

"I never in a million years could have believed Devin could be capable of this kind of thing," Ivey said.

"My family will suffer because of his coward actions."

Cars lined the highway outside the house at 2825 FM 2722 on Monday morning. A truck from the Comal county sheriffs department blocked the property's gate, which was adorned with a "beware of dog" sign.

Doug, who lives across the street and declined to give his last name, said he didn't get to know the family at all, in the 11 years he lived on the road.

"The only time I see them is when they're going out and they don't even look my way," he said. He said he didn't recognise the shooter at all.

He said he regularly heard gunshots coming from the property across the street but thought little of it. The noise used to shake his two small dogs, Scholtz and Gretchen, he said.

Mark Moravitz, who lives across the street from the Kelley family, also said he frequently heard gunfire coming from the property, often around 10 or 11pm.

"We hear a lot of gunfire a lot," he told KSAT, "but we're out in the country."

Reached by phone Sunday night, several other Neighbours told The Washington Post that they didn't know the Kelley family but noted that several ranches in the area allow hunting. The sound of gunshots isn't unusual, they said.

Moravitz told local media that the Kelley family travelled frequently, so he would house sit for them. He described Kelley as a "regular guy" and said it was "shocking" to hear about the shooting.

"You never think your neighbour is capable of something like that," he said. "If he did that, that kind of worries you, thinking we've been living next door to the guy."

Other Neighbours told KENS 5 that they would sometimes see couches, bicycles, lawn mowers and other household items along the street in front of the property, placed there as if they were free for the taking.

Officials described the shooter's weapon as a Ruger AR-556, an assault-style rifle similar to those used by the military. CNN, citing a law enforcement individual, reported that Kelley purchased the weapon in April 2016 from an Academy Sports & Outdoors store in San Antonio.

A Facebook page bearing Kelley's name showed a photo of a Ruger assault-style rifle. The page was taken down at some point on Sunday. The Los Angeles Times reported that in recent months Kelley had started adding strangers from the Sutherland Springs area as Facebook friends and picking fights with them.

Johnathan Castillo told the Times that he accepted Kelley's friend request a couple months ago, but deleted it soon after. Castillo said of Kelley: "It's like he went looking for it, you know what I mean?"

Attempts to reach members of Kelley's immediate family were unsuccessful late Sunday night.

During the evening, Texas Rangers and a K-9 vehicle were staked out in front of the family's house, according to local media. Deputies were reportedly guarding the entrance to the home.