The shooting occurred about 8 a.m. at Lakeview and Mariposa avenues, and a handgun was recovered at the scene, according to Orange County sheriff's Lt. Mark Stichter.
The victim, who was not immediately identified, was airlifted to Orange County Global Medical Center in Santa Ana. A condition report was not available, but the victim was shot in the chest, according to Stichter.
Jack Horn Jr., 73, was booked on suspicion of assault with a deadly weapon, according to the Sheriff's Department.
It's unclear what relationship, if any, the two had, Stichter said, adding they were not transients.