A Christian couple who lost eight members of their family - including their pastor son - in a Texas church shooting has filed a legal claim with the US Air Force, saying the military branch is partially responsible for their deaths.

Joe and Claryce Holcombe say the Air Force's failure to report gunman Devin Kelley's criminal convictions, arrest, and military discharge information to an FBI database used to check backgrounds of gun buyers helped cause the massacre in Sutherland Springs that left more than two dozen dead, reports KSAT.

The claim, filed Tuesday, state the deaths were caused "in whole or in part by the institutional failures of the United States Department of Defense, including, but not limited to the United States Air Force."

"Although the shooter undoubtedly 'pulled the trigger' that resulted in the injuries and death of JB Holcombe and others, failures of the US Air Force, and others, allowed the shooter to purchase, own and/or possess the semiautomatic rifle, ammunition and body armor he used, and it is these failures that were a proximate cause, in whole or in part, of the injuries and death of the decedent," reads the claim.

The Holcombe's 60-year-old son, Bryan Holcombe, was walking up to the pulpit, preparing to lead the congregation in worship, when Kelley began to spray bullets at the worshipers.

Bryan Holcombe, an associate pastor for the church, was killed in the gunfire, along with his wife, Karla, son Marc Daniel, and one-year-old granddaughter, Noah.

Another son of Bryan and Karla, John Holcombe, survived, but his wife, Crystal Holcombe, who was pregnant, did not. Three of Crystal's five children were also killed.

Kelley, who killed a total of 26 people in what has been described as the worst mass shooting in Texas history, had a history of domestic violence and was given a bad conduct discharge from the Air Force after pleading guilty to assaulting his first wife and stepson.

Under federal law, anyone convicted of domestic violence cannot purchase a firearm; however, Kelley, according to an official with the Bureau of Alcohol, Tobacco, Firearms and Explosives, purchased a gun in 2014, 2015, 2016 and 2017.

The Air Force has since acknowledged it failed to submit Kelley's criminal history to the FBI, blaming "failures in training and compliance measures," and said it has taken corrective actions to prevent such reporting lapses.

Joe Holcombe told KSAT the Air Force made a "terrible mistake." 

"We want to discipline the Air Force so that something like this is not going to happen again," he said.

On November 15, three thousand people mourned the eight members of the Holcombe family, releasing light pink and blue balloons at a graveside service.

Joe and Claryce Holcombe told the Washington Post that their son Bryan had been involved in church work since he was young.

"We knew when he was born that he was going to be a preacher," Joe said, revealing his first word was "God" and his first sentence was "See the light."

While the Holcombes are still coming to terms with what happened, they're confident their family members are in Heaven - and the shooter is "being rewarded right now for what he did, and for all of eternity."

Claryce added, "we need to pray for his family, because they're going through a terrible time, too."

"It's of course going to be difficult," Joe Holcombe said.

But, he said, "we are Christians; we have read the book. We know the ending, and it's good...God will see us through. We'll all be together soon."