The Texas worshipper who shot and killed a gunman who opened fire in a church killing two during a busy Sunday service says he did not want "evil to succeed".

Jack Wilson, 70, head of security at West Freeway Church of Christ, posted a statement on Facebook saying he "had to take out" the shooter because "evil exists".

The service in the suburbs of Fort Worth was being livestreamed to social media, and showed the moment of the attack when the gunman, wearing a coat, started shooting with a shotgun.

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

Keith Thomas Kinnunen is the shooter from Sunday's Texas church shooting. Photo / Supplied.
Keith Thomas Kinnunen is the shooter from Sunday's Texas church shooting. Photo / Supplied.

Wilson, who is running for county commissioner in the area, said he was grateful he had the chance to defend himself and fellow worshippers from the "evil" gunman.

"I'm thankful to God that 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 brother in Christ, but evil does exist in this world and I and other members are not going to allow evil to succeed," he said.

Speaking to local reporters, Wilson said he did not consider himself a hero.

Police identified the gunman as Keith Thomas Kinnunen, 43. He had a criminal past involving theft and aggravated assault with a deadly weapon.

The two people killed were a security guard and a grandfather, Anton "Tony" Wallace, who had just handed out communion.

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

Wilson describes himself as a former sheriff and small business owner on Facebook. He has been married for 51 years, has three daughters and some grandchildren.

Wallace's adult daughter Tiffany watched in horror from her pew as her father was shot. She revealed in an interview on Sunday night that she ran towards him as he took his last breaths.


"I ran toward my dad and the last thing I remember is him asking for oxygen and I was just holding him, telling him I loved him and that the was going to make it," she told NBC.

The other victim who died has not yet been named.

Mike Tinius, an elder at the church, told New York Times Wallace was a dear friend.

"He was trying to do what he needed to do to protect the rest of us," Tinius said.

"It's extremely upsetting to see anyone committing violence."

The FBI is investigating the shooting. They said Kinnunen was "relatively transient" but was known to have connections to the area. His motives remains unknown.