Police praised the "exceptional heroism" of the pastor and the church members, mostly pensioners of Taiwanese descent, after they managed to overpower the shooter on Sunday afternoon.

The pastor hit him over the head with a chair as he stopped to reload his gun at Geneva Presbyterian Church in the city of Laguna Woods and churchgoers bound up his legs with electrical cord.

The motive for the shooting remains unclear, but investigators do not believe the gunman, an unnamed Asian man in his 60s, lives in the area.

The shooter fired inside the church as members ate lunch after a morning service.

Of the victims who survived the attack, four were critically injured and one suffered minor injuries.

Four were Asian men aged from 66 to 92 and one was an 86-year-old Asian woman.

The shooting came only a day after an 18-year-old gunman killed 10 people at a supermarket in Buffalo, New York, in a what officials described as a racially motivated attack.

One member of the church, Jerry Chen, 72, was in the kitchen when he heard gunshots from the hall.

He looked around the corner to find members screaming, running and hiding under tables.

"I knew someone was shooting," he said. "I was very, very scared. I ran out the kitchen door to call 911."

Mr Chen said he was in a state of shock and could not tell the operator his location, adding he had "to ask someone else for the address".

'It could have been much worse'

A group of about 40 worshippers had gathered for lunch with their former pastor, Billy Chang, who moved back to Taiwan two years ago after serving the church for two decades.

"Everyone had just finished lunch," Mr Chen said.

"They were taking photos with Pastor Chang. I had just finished my lunch and went into the kitchen."

Mr Chen said his fellow worshippers told him that Pastor Chang had hit the gunman over the head with a chair.

"It was amazing how brave he and the others were," he said.

"This is just so sad. I never, ever thought something like this would happen in my church, in my community."

Most of the members are elderly, highly educated Taiwanese immigrants, he added.

Read more from Sky News on the Buffalo shooting:
Victims of supermarket shooting named
Gunman was a 'sick, demented individual'
Shooter livestreamed 'racially motivated' mass shooting

Jeff Hallock, undersheriff in the Orange County sheriff department, said: "That group of churchgoers displayed what we believe is exceptional heroism and bravery in intervening to stop the suspect.

"They undoubtedly prevented additional injuries and fatalities. I think it's safe to say that had people not intervened, it could have been much worse."