Officers said a group was gathering outside after a young adults meeting when someone started shooting. An 18-year-old and a 19-year-old were shot.
Both men were taken to the hospital and are expected to survive.
Investigators said they don't know if the victims were targeted or randomly shot. There is no word on any suspects.
Anyone with information on the shooting is asked to call the Ontario Police Department at (909) 395-2001.