Officers got a call about 12:45 p.m. from Watsonville Fire Department firefighters who had been headed back to the station after a call when they were flagged down by a person who told them the traffic signal had gone through several cycles but the Cadillac hadn't moved, Sgt. Henry Robles said.
Authorities found a man slumped over the wheel with a handgun in his lap, he said.
The man was alive, and was flown to a Santa Clara County trauma center with life-threatening injuries, Robles said.
He appeared to be in his 20s and lives locally, he said.
Detectives were still canvassing the area for witnesses and working on the case later Saturday afternoon and Robles said he had not yet received an update on the man's condition.