San Jose police answered a call about a possible dead person at 3:39 a.m. near Fourth and Julian streets and located a man in his late 70s to early 80s inside the vehicle, police Officer Albert Morales said.
The man was unresponsive and pronounced dead at the scene by medical personnel, Morales said.
Based on a preliminary investigation, police believe the man did not die of natural causes and the department's Crime Scene Unit arrived and collected potential evidence, Morales said.
The Santa Clara County medical examiner's is conducting an autopsy to determine the cause of death, Morales said.
A spokeswoman for the medical examiner's office said this morning that the office was not ready to release information about the man.
