A gunman who killed two people during a Texas church service was fatally shot within seconds by armed congregants, said Texas officials, who hailed the state's gun laws that allow weapons in places of worship.

More than 240 parishioners were in the West Freeway Church in the Fort Worth area town of White Settlement at the time of the shooting on Sunday, authorities said.

Parishioner Isabel Arreola told the Star-Telegram that she sat near the gunman and that she'd never seen him before Sunday's service. She said he appeared to be wearing a disguise, perhaps a fake beard, and that he made her uncomfortable.

She said the man stood up, pulled a shotgun from his clothing, opened fire and was quickly shot by two congregants who were part of a volunteer security team.

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

Tiffany Wallace told Dallas TV station KXAS that her father, Anton “Tony” Wallace, was one of the victims killed in the attack. She said her father was a deacon at the church and had just passed out communion when the gunman approached him.

“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.

Wallace said her father was rushed to a hospital but he did not survive.

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

At a press conference Sunday night, Texas Lt. Gov. Dan Patrick said the gunman was killed within six seconds of opening fire. Patrick hailed the state's gun laws, including a measure enacted earlier this year that allowed licensed guns in places of worship, unless the facility bans them.

"Two of the parishioners who were volunteers of the security force drew their weapons and took out the killer immediately, saving untold number of lives," Patrick said.

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

Officials have not released the names of the victims or the gunman. FBI Special Agent in Charge Matthew DeSarno said they're working to identify the gunman's motive, adding that he is “relatively transient” but had roots in the area.

DeSarno also said the gunman had been arrested multiple times in the past but declined to give details.

An elder at the church told the New York Times that one of those killed was a security guard who responded to the shooter, calling him a dear friend.

“He was trying to do what he needed to do to protect the rest of us,” said the elder, Mike Tinius.

“It’s extremely upsetting to see anyone committing violence,” he said.

Tinius said he didn't know the gunman and that the shooting appeared to be random.

A woman who answered the phone at the West Freeway Church of Christ told the AP she could not answer any questions and that she was told to direct inquiries to authorities.

In a livestream of the church service, the gunman can be seen getting up from a pew and talking to someone at the back of the church before pulling out a gun and opening fire. Parishioners can then be heard screaming and seen ducking under pews or running as papers fly to the floor.

Two people with minor injuries that were sustained while ducking for cover were treated at the scene, MedStar Mobile Healthcare spokeswoman Macara Trusty said.

Gov. Greg Abbott asked the state to pray for the victims, their loved ones and the community of White Settlement, about 8 miles (12 kilometers) west of Fort Worth.

“Places of worship are meant to be sacred, and I am grateful for the church members who acted quickly to take down the shooter and help prevent further loss of life,” Abbott said in a tweeted statement.

It is not the first deadly shooting to take place at a church in Texas. In November 2017, Devin Patrick Kelley opened fire on the congregation at a church in Sutherland Springs, killing more than two dozen worshippers, before taking his own life. And in 1999, a gunman killed seven people in Wedgwood Baptist Church in Fort Worth before detonating an explosive device and killing himself.

Sunday's shooting in Texas was also 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.