At least two people have been killed and a third is in critical condition after a shooting at a church in the suburbs of Fort Worth, Texas in the United States.

One person died at the scene of the shooting and another passed away while en route to a local hospital, the Dallas Morning News said, citing a spokeswoman for local emergency services.

Authorities rushed to the scene at White Settlement, a suburb northwest of Fort Worth, where the West Freeway Church of Christ is located.

It's believed the man opened fire inside during a service at around 11.30am local time on Sunday (4.30am AEDT).

The service was being livestreamed on YouTube when the attack unfolded and a screenshot of the vision shows worshippers ducking for cover.

It appears that an armed person who was in attendance stood up and shot the attacker.

The Fort Worth Fire Department issued an "active threat" assignment and was assisting operations at the scene, according to reports.

A witness told a local CBS affiliate that a man armed with a shotgun walked up to a server during communion and opened fire, before being shot by a person attending the service.

"You feel like your life is flashing before you. I was so worried about my little one," witness Isabel Arreola told the network.

RELATED: Attacker storms rabbi's home and stabs five during Hanukkah celebrations

Authorities believe the attacker was among the three people shot but it was not known whether he had been killed or injured, CBS 11 reported.

The shooting was captured on video as the church service was being streamed on YouTube, according to the New York Daily News.

More to come …

Reuters