The gunman stood up from a pew at West Freeway Church of Christ in White Settlement, a suburb of Fort Worth, pulled out a shotgun and began firing.

A motive has not been established for the shooting, which lasted six seconds.

White Settlement police chief JP Bevering praised "the heroic actions" of those who confronted the attacker.

The shooting took place at about 11:50 (17:50 GMT) on Sunday, during a morning service that was being livestreamed on social media.

Video footage showed the gunman stand up from a pew and speak to a man nearby, who gestured at another parishioner. The gunman then fired at the man he gestured towards.

The gunman fired again, at the man he had spoken to, before a member of the congregation acting as a security guard returned fire with a handgun, immediately felling the attacker.

Several other parishioners also produced handguns and trained them on the attacker. It was not clear from the video footage whether any of the other armed parishioners fired shots.

The two churchgoers who were shot died later in hospital, police said.

The shooting happened during the morning service at West Freeway Church of Christ

Authorities have not yet released the names of the two parishioners who were killed or the gunman.

Members of the congregation in the nearly full church were seen on the livestream ducking down behind pews as screaming filled the room.

Jack Cummings, a minister at the church, told the New York Times that the gunman had been "acting suspiciously" and drew the attention of the church's security team.

The security team is made up of volunteers from the church's membership who are licensed to carry firearms. "They saved a lot of lives today because this thing would have been a massacre otherwise," Mr Cummings said.

A member of the security team was killed in the attack, he added.

Church elder Mike Tinius told the newspaper he had known that victim for more than 20 years. "He was trying to do what he needed to do to protect the rest of us," he said.

Texas Governor Greg Abbott called the shooting "an evil act of violence".

"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," he said in a statement.

Witness Isabel Arreola told local broadcaster CBS DFW: "It was the most scariest thing. You feel like your life is flashing before you. I was so worried about my little one."

Shocked worshippers were evacuated from the church

In September, a new law came into effect in Texas that allowed licensed handgun owners to carry weapons in places of worship.

The state has seen a number of deadly shootings this year. In August, 22 people died and 24 were wounded at a Walmart store in El Paso. The same month a gunman killed seven and wounded 20 at Odessa-Midland.

In 2017, 26 people were killed when a gunman opened fire at a Baptist church in Sutherland Springs, Texas, during a Sunday service.