Chino police said two groups at the Prado Regional Park campground got into a drunken argument about loud music early Sunday and one man from each group drew a gun and fired, the Los Angeles Times reported Tuesday.
Police said the men, Dejay Barber, 44, and Matthew Rincon, 24, both turned out to be off-duty Los Angeles County sheriff's deputies. The men did not know they were co-workers until after the incident, police said.
Barber and Rincon were arrested on suspicion of negligent discharge of a firearm.
Sheriff's spokesman Steve Whitmore said the men have been relieved of duty with pay. He said the men fired their guns into the air, not at other people.
"Alcohol is suspected," Whitmore said. "This is gross negligence."
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