Bailey LeJeaune, 17, and David Betancourt, 18, hold candles during a vigil in Sutherland Springs for the victims of a deadly shooting at the First Baptist Church in Sutherland Springs, Texas. Picture: Jay Janner/Austin American-Statesman via AP

New Braunfels — The man authorities have identified as the gunman in a mass shooting at a Texas church was discharged from the Air Force for allegedly assaulting his spouse and child, according to an Air Force spokesperson.

The spokesperson, Ann Stefanek, said Sunday that Devin Kelley served 12 months' confinement after a 2012 court-martial. He ultimately received a bad conduct discharge and reduction in rank.

She said Kelley served in Logistics Readiness at Holloman Air Force Base in New Mexico from 2010 until his discharge in 2014. His job responsible for moving passengers, cargo and personal property in military transportation.

Authorities did not announce his name at a news conference on the shooting, saying only that the suspect was a white male in his 20s.

But a US official and a law enforcement official identified Kelley as the person who opened fire Sunday at the First Baptist Church of Sutherland Springs, Texas, killing 26 people and wounding about 20 others.

The US official told The Associated Press that Kelley lived in a San Antonio suburb and that he doesn't appear to be linked to organised terrorist groups. 

The official said investigators are looking at social media posts Kelley may have made in the days before Sunday's attack, including one that appeared to show an AR-15 style semi-automatic weapon. The official requested anonymity because the person did not have authorisation to speak publicly.

An address listed in online records as belonging to Kelley is located in New Braunfels, Texas, just outside San Antonio and about 35 miles (56 kilometres) from Sutherland Springs.

Local records of an August traffic ticket issued in New Braunfels, Texas, for an expired registration and not having auto insurance give a birthdate that would make him 26 years old.

At the address listed for Kelley in New Braunfels, two sheriff's vans were parked outside and police officers stood at the gate of a cattle fence surrounding the property. 

Law enforcement officials gathered at the property declined to comment on why they were there. Several messages left for his relatives went unreturned.

Neighbours said that they heard intense gunfire coming from the direction of the address listed for Kelley in recent days.

"It's really loud. At first I thought someone was blasting," said Ryan Albers, 16, who lives across the road. "It had to be coming from somewhere pretty close. It was definitely not just a shotgun or someone hunting. It was someone using automatic weapon fire."

A person matching Kelley's name and date of birth also registered in 2014 to vote in Colorado, with an address listed in Colorado Springs, home of the US Air Force Academy. The Colorado Secretary of State's office lists his registration now as inactive.

According to Texas Department of Public Safety regional director Freeman Martin, the gunman arrived at a Valero gas station near the First Baptist Church of Sutherland Springs at around 11:20 a.m. Sunday. He was dressed in black, wearing tactical gear and a ballistic vest.

He crossed the street to the church, left his vehicle and started firing a Ruger AR assault-type rifle at the church. Then he entered the church and fired.

As he left the church, the shooter met an unidentified area resident with his own rifle who pursued him. The suspect was found dead in his vehicle near the border between Wilson and Guadalupe counties.

Martin says it's unclear if he died of a self-inflected wound or was shot by the resident.

Associated Press