The shooting occurred at a lunch banquet after a service at the Geneva Presbyterian Church.
According to Orange County police, one of the victims died on the spot, four are critically injured and one has minor injuries.
All victims are adults.
There were about 30-40 people in the room when the perpetrator attacked.
The alarm came at 13.26 local time and led to a large increase.
- We believe that a group of churchgoers held him, tied him with an electric cord and confiscated two weapons.
He was detained when police arrived at the scene, said Jeff Hallock of the Orange County Police Department at a news conference, and continues:
- The group of churchgoers gave evidence of what we believe was exceptional heroism and courage when they intervened to stop the suspect, their efforts undoubtedly led to fewer injured and dead.
Older perpetrator
The detainee is a man in his 60s who is not believed to belong to the church or live nearby.
- We do not know what the suspect's motive may have been, or if he had a designated target or if it is even a hate-related incident, Hallock says.
The seized weapons are two handguns, according to police.