White Settlement: A man pulled out a shotgun at a Texas church service and killed two people before he was fatally shot by congregants who quickly returned fire, police say.

Authorities praised the two congregants who opened fire as part of a volunteer security team at West Freeway Church of Christ in White Settlement, about 12 kilometres west of Fort Worth.

In this still frame from livestreamed video provided by police, churchgoers take cover while a congregant armed with a handgun (top left) engages a man who opened fire (near top centre just right of windows) during a service at West Freeway Church of Christ in White Settlement, Texas. Credit:AP

"This team responded quickly and within six seconds, the shooting was over. Two of the parishioners who were volunteers on the security force drew their weapons and took out the killer immediately, saving untold number of lives," said Lieutenant Governor Dan Patrick, who also hailed the state's gun laws at a news conference on Sunday evening (Monday morning AEDT).

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