President Trump offered gratitude to the congregants who stopped a shooter at a Texas church Sunday morning, saying the attack that left two parishioners dead would have been far worse if none of the worshippers had been armed.

A gunman opened fire at West Freeway Church of Christ in White Settlement, killing two of the 240 people present, but he was fatally shot almost immediately when two congregants fired back.

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"Armed congregants quickly stopped a crazed church shooter in Texas. If it were not for the fact that there were people inside of the church that were both armed, and highly proficient in using their weapon, the end result would have been catastrophic," Trump tweeted Tuesday morning. "A big THANK YOU to them!"

Jack Wilson, one of the churchgoers who stopped the gunman, shared some details on Facebook, saying that circumstances "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."

Wilson, who is running for commissioner for the 3rd Precinct, is head of the church's security team and a firearms instructor. He said Monday that when the gunfire began, there were people initially in between him and the shooter who stood up, and that he wanted to make sure he didn't hit a member as they were right in front of him.

Video of the incident shows parishioners quickly ducking behind pews, giving Wilson a better opportunity to take action.

"I had a clear shot and I was comfortable taking the shot," Wilson said.

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Within 6 seconds, the gunman was down after Wilson fired one round. He told reporters he then pulled the shotgun away from the man's body and stood over him in case the shooter tried to get up, which he did not.

During a news conference later Sunday, Lt. Gov. Dan Patrick lauded the quick reactions of the church’s "well-trained" security team, calling their heroism "unparalleled."

Wilson said preparation is key for those who decide to arm themselves.

"You have to be prepared at all times, at all places," he said. "And that's what I strive, that's the way I teach, that's the way I want people to understand if they are going to wear a firearm for personal protection for themselves, or family, or anyone else they need to be aware that it can happen anytime, anywhere."

Fox News' Travis Fedschun, Bradford Betz and The Associated Press contributed to this report.