The Los Angeles County Sheriff's Department sent an alert just before 2 p.m. saying, "DANGER: Active search for vicious pit bull dogs."
David Sommers, public affairs director for the Los Angeles County Chief Executive Office, told NBC-TV, Los Angeles, helicopters were being used in the search to aid animal control vehicles in the area.
At least four animals were taken from a home near the scene of the mauling at about 5 p.m., the TV station said, but it wasn't clear if they were the dogs involved.
County Supervisor Mike Antonovich announced a $25,000 reward for information leading to the capture of the killer dogs.
A witness driving on Avenue S saw the victim on the ground surrounded by the pack of dogs and called 911 at about 9:30 a.m.
One dog was still on the scene when a deputy arrived, and the animal charged.
"He tried to chase the dog off; the dog charged the deputy. That's when the deputy shot at the dog," sheriff's Lt. John Corina said."As far as we know, he didn't hit the dog. So we're in the process of looking for these four dogs that are running around out here in the desert."
The victim, who was not identified, died in an ambulance, Los Angeles County Chief Executive Officer Bill Fujioka said.