The security guard who shot dead a gunman after he opened fire during Sunday service at a Texas church has thanked God.

Keith Thomas Kinnunen, 43, was identified by authorities as the gunman who launched a shooting attack at West Freeway Church of Christ in White Settlement, Texas, killing two. 

Security guard Richard White, 67, and grandfather Anton "Tony" Wallace, 64, were both killed in the shooting, which happened moments after they assisted in delivering the communion. 

Kinnunen was stopped by Jack Wilson, a 71-year-old firearms instructor. 

On Facebook, he explained why he had shot the gunman and asked for prayers for everyone affected by the tragedy. 

"The events at West Freeway Church of Christ put me in a position that I would hope no one would have to be in, but evil exists and I had to take out an active shooter in church," he said. 

"I'm thankful to GOD that I have been blessed with the ability and desire to serve him in the role of head of security at the church.

"I am very sad in the loss of two dear friends and brothers in CHRIST, but evil does exist in this world and I and other members are not going to allow evil to succeed.

"Please pray for all the members and their families in this time. Thank you for your prayers and understanding."

In comments to NBC News, Wilson said he had shot the gunman because he feared he would shoot more people. 

"I don't feel like I killed a human," he said. "I feel like I killed an evil. That is how I am coping with the situation."

It is not the first time that a Texas church has been the victim of a deadly shooting. 

In November 2017, 26 people, including the pastor's daughter, were killed when a gunman walked into the First Baptist Church in Sutherland Springs.  In that attack, the gunman was also shot by an armed civilian.