Witnesses said a group of people were leaving an event when shots rang out, hitting four of them.
Long Beach police officials said the gunman got out of a vehicle, opened fire, got back into the car and sped away.
"I saw the cops over there and people walking to look for a body down there," said Marcus Falanai, who witnessed the incident.
Police said the shooting may be gang related.
A bishop of the religious school said there was a party on the second floor of the college building, but the party was not affiliated with the school.
The victims were at a banquet hall that was rented out for the night.
"As far as people from our church being involved, I don't think so," said Bishop Gus Ahkiong of the Sure Foundation Church of God. "I think it's got to be someone from outside."
A description of the vehicle was not available.
The victims were taken to a nearby hospital for treatment. Authorities said their injuries are not life-threatening.
Anyone with information is being asked to call Long Beach police at (562) 435-6711.