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MIAMI (CBSMiami/CNN) — The man accused of killing more than two dozen people at a church in Texas was once a U.S. Air Force member.

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Law enforcement briefed on the investigation into the deadly mass shooting at First Baptist Church in Sutherland Springs identified the shooter as Devin Patrick Kelley, 26.

The said he had domestic problems, and his mother-in-law had attended the church he targeted Sunday, said Freeman Martin of the Texas Department of Public Safety.

Kelley’s mother-in-law had received threatening messages from him, Martin said.

What we know about the shooting

As a U.S. Air Force member, he served in logistics readiness at Holloman Air Force Base in New Mexico, starting in 2010, according to spokeswoman Ann Stefanek.

Kelley was court-martialed in 2012 for two counts of Article 128 of the Uniform Code of Military Justice, assault on his spouse and assault on their child, Stefanek said. Kelley received a bad conduct discharge, confinement for 12 months and a reduction in rank, she said. The Air Force did not provide a date of the discharge.

Kelley is accused of killing 26 people, including the 14-year-old daughter of the church’s pastor, and injuring more.

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A man who lives next door to the church grabbed his own gun and approached Kelley as he was leaving after the shooting. The gunman dropped a rifle in front of the church and fled in his car, officials said.

Kelley was found dead in his car from a gunshot wound about eight miles from the church, a law enforcement official briefed on the investigation told CNN.

He called his father after he was shot by a civilian and told his father he didn’t think he was going to make it, said Martin.

Kelley then shot himself, Martin said.

He purchased the Ruger AR-556 rifle in April 2016 from an Academy Sports & Outdoors store in San Antonio, a law enforcement official told CNN.

When Kelley filled out the background check paperwork at the store, he checked the box to indicate he didn’t have disqualifying criminal history, the official said. He listed an address in Colorado Springs, Colorado when he bought the rifle, the official said.

Kelley did not have a license to carry, authorities said.

Deadly mass shootings in modern US history

Texas Gov. Greg Abbott called the incident the largest mass shooting in the state’s history.

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(©2017 CBS Broadcasting Inc. All Rights Reserved. CNN contributed to this report.)