Arriving officers found the veteran investigator with one gunshot wound to the chest.
Officials said he was able to speak with first responders. They determined that it was likely a self-inflected gunshot wound, possibly accidental.
"Initial investigation determined that we found a weapon nearby that we believe belonged to the investigator," said Ventura police Cmdr. David Wilson. "We are still determining what actually happened during the shooting."
Wilson said an accidental shooting was "one angle we're looking at."
The investigator's name has not been released.
Police said the investigation is ongoing. However, detectives said they believe there are no outstanding suspects.