The victim was being attacked by at least two dogs when the good Samaritan rammed his van through a chain-link fence and scared the dogs away, the Los Angeles Times reported.
The incident occurred at 4:15 p.m. Tuesday.
The victim was taken to the hospital with serious injuries.
One dog was owned by the victim, and the other was owned by his roommate, the Riverside County Department of Animal Services said.
The roommate approved his dog to be euthanized after the attack, the Times said.
Officials said the investigation is ongoing, but it appears that the victim was trying to break up a fight between the two dogs.