A Northern California university police chief repeatedly stabbed his stepson in the chest with a power drill and fired a warning shot after an argument turned into a fight, authorities have said.

Nathan Johnson, the top cop from the Sonoma State University force, was treated for a cut on his head after getting into a brawl with Elijah Latimer.

The 20-year-old went to a hospital with multiple stab wounds and an apparent punctured lung.

Nathan Johnson, the chief of the Sonoma State University police force in California reportedly stabbed his stepson, Elijah Latimer, 20, in the chest with a power drill after firing at him

Sheriff's Sgt. J.D. Nelson told the San Francisco Chronicle investigators are trying to determine what led to Monday's fight.

He said: We’ve got a ton of conflicting stories, so it’s kind of hard to sort everything out.

'They had some sort of an argument, we know that, but how it escalated into a stabbing with a drill and gunplay is the million-dollar question.'

Reports suggest neither of them wanted to file a criminal complaint.

Johnson, who couldn't be reached for comment, told investigators he fired his personal gun into a wall as a warning.

The school with more than 9,000 students is an hour north of San Francisco.