Alarms went off in Jack Wilson's head the moment a man wearing a hat, long coat and wig walked into a Texas church for Sunday services.

By the time the man approached a communion server and pulled out a shotgun, Wilson and another security volunteer were already reaching for their own guns.

The attacker shot the other volunteer, Richard White, and then the server, Anton "Tony" Wallace, sending congregants scrambling for cover. The gunman was heading toward the front of the sanctuary as Wilson searched for a clear line of fire.

"I didn't have a clear window because I had members that were jumping, going chaotic," said Wilson, a 71-year-old firearms instructor who has also been a reserve sheriff's deputy. "They were standing up. I had to wait about half a second, a second, to get my shot. I fired one round. The subject went down."

Wilson's single shot quickly ended the attack that killed Wallace, 64, and White, 67, at the West Freeway Church of Christ in the Fort Worth-area town of White Settlement. He said the entire confrontation was over in no more than six seconds. More than 240 congregants were in the church at the time.

"The only clear shot I had was his head because I still had people in the pews that were not all the way down as low as they could. That was my one shot," Wilson said Monday from his home in nearby Granbury.

As Wilson approached the fallen attacker, he noticed five or six other members of the volunteer security team he had trained with their guns drawn. Wilson said they had their eyes on the man since he arrived. During the service, White and Wilson had stationed themselves at the back of the church, watching him.

'I killed an evil.' Jack Wilson describes what happened when he shot a gunman who attacked a Texas church. 1:51

'It could have been a lot worse'

The Texas Department of Public Safety on Monday identified the attacker as Keith Thomas Kinnunen, 43. His motive is under investigation.

Speaking outside the church Monday, Texas Attorney General Ken Paxton said authorities "can't prevent mental illness from occurring, and we can't prevent every crazy person from pulling a gun. But we can be prepared like this church was."

Britt Farmer, senior minister of the church, said, "We lost two great men today, but it could have been a lot worse."

Wilson described the attacker's gun as a short-barrelled 12-gauge shotgun with a pistol grip. Shotguns with barrels less than 18 inches long are restricted under U.S. federal law and can be legally owned in Texas only if they are registered with the Bureau of Alcohol, Tobacco, Firearms and Explosives.

State's gun laws praised

After the shooting, Texas officials in hailing the state's gun laws, including a measure enacted this year that affirmed the right of licensed handgun holders to carry a weapon in places of worship, unless the facility bans them.

U.S. President Donald Trump also tweeted his appreciation for the state's gun legislation Monday night, saying, "Lives were saved by these heroes, and Texas laws allowing them to carry arms!"

That law was passed in the aftermath of the deadliest mass shooting in Texas history, which was also at a church. In the 2017 massacre at First Baptist Church of Sutherland Springs, a man who opened fire on a Sunday morning congregation killed more than two dozen people. He later killed himself.

Isabel Arreola told the Fort Worth Star-Telegram that she sat near the gunman and she had never seen him before the service. She said he appeared to be wearing a disguise and he made her uncomfortable.

"I was so surprised because I did not know that so many in the church were armed," she said.

Sunday's shooting was the second attack on a religious gathering in the U.S. in less than 24 hours. On Saturday night, a man stabbed five people as they celebrated Hanukkah in an Orthodox Jewish community north of New York City.

Victims remembered

Wallace's daughter, Tiffany Wallace, told Dallas TV station KXAS that her father was a deacon at the church.

"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 he was going to make it," Wallace said.

"You just wonder why? How can someone so evil, the devil, step into the church and do this," she said.

White's daughter-in-law, Misty York White, called him a hero on Facebook: "You stood up against evil and sacrificed your life. Many lives were saved because of your actions. You have always been a hero to us but the whole world is seeing you as a hero now. We love you, we miss you, we are heartbroken."

Motive still under investigation

The FBI was working to determine the shooter's motive. Special Agent in Charge of the Dallas office, Matthew DeSarno, said the assailant was "relatively transient" but had roots in the area.

Paxton said Monday that the shooter appeared to be "more of a loner." "I don't think he had a lot of connections to very many people," he said.

Investigators searched Kinnunen's home in River Oaks, a small nearby city where police said the department's only contact with the suspected gunman was a couple of traffic citations. But Kinnunen appeared to have more serious brushes in other jurisdictions. He was arrested in 2009 on charges of aggravated assault with a deadly weapon in Fort Worth and in 2013 for theft, according to Tarrant County court records.

He was arrested in 2016 in New Jersey after police allegedly found him with a 12-gauge shotgun and rounds wrapped in plastic in the area of an oil refinery, according to the Central New Jersey Home News in East Brunswick. It was not immediately clear how those charges were resolved.

In a 2009 affidavit requesting a court-appointed attorney, Kinnunen listed having a wife and was living with four children, according to court records. He told the court he was self-employed in landscaping and irrigation work.

White Settlement's website says it was named by local Native Americans in the 1800s for white families then settling in the area. City leaders who worried that the name detracted from the city's image proposed renaming it in 2005, but voters overwhelmingly rejected the idea.

Security team started 18 months ago

Wilson said the church started the security team about 18 months ago after they moved to a new building and became concerned about crime in the area. Wilson has been a firearms instructor since 1995, spent six years in the Army National Guard and was a Hood County reserve deputy. He said some of the security team members he trained were at first even afraid to touch a firearm.

"We were aware that it could happen. Most team members there didn't feel like it would happen, but we were prepared if it did," he said.

Wilson said the congregation is a close-knit group.

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