The Alameda County Sheriff's Office says one of its deputies was arrested in Livermore last week.
Gael Paredes, 27, is accused of DUI and battery after crashing his personal car on someone's property then attacking that homeowner.
The homeowner tells NBC Bay Area Paredes tried to run away after the crash and when he tried to stop him, the deputy punched him in the face. The victim, a retired police officer, said he suffered a minor concussion after the attack.
Paredes was booked into Santa Rita Jail in Dublin.
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A spokesperson for the Alameda County Sheriff's Department said they were aware of Paredes' arrest and the deputy is currently on leave.
"The criminal allegations are serious and being handled appropriately by the judicial system," the spokesperson said. "This is a personnel matter and we will not comment further."