RICHMOND (CBS SF) — A Walnut Creek police officer arrested in Richmond earlier this month after allegedly donning a mask and beating a woman with a baseball bat has been placed on administrative leave, police said Friday.

Gregory Thompson, 53, of Martinez, was arrested in the early morning hours of Aug. 16 in Richmond, where he allegedly used a bat to attack a woman walking in a residential neighborhood, according to Richmond police Capt. Bisa French.

Contra Costa County prosecutors are reviewing the case and expect to make a decision about possible charges next week, said Deputy District Attorney Barry Grove said, who declined to comment further on the case.

Walnut Creek police Capt. Mark Perlite said Thompson was placed on administrative leave immediately after the department learned of his arrest.

Perlite said Thompson is a 30-year veteran of the police department and was most recently working as a patrol officer.

Walnut Creek police are conducting their own investigation into Thompson’s arrest, he said.

The arrest happened after police received multiple reports around 2 a.m. on Aug. 16 of a woman screaming and a man with a bat in the 4000 block of Clinton Avenue, according to French.

She said when officers arrived on the scene, a witness pointed out Thompson, who was sitting inside his parked car.

He was not wearing a police uniform or in a police patrol car at the time of the alleged assault.

While speaking with Thompson officers noticed a mask on the vehicle’s floorboard. A search of the car also turned up a bat, two guns and zip ties, she said.

Thompson, who identified himself as a police officer, was arrested on suspicion of assault with a deadly weapon, criminal threats and felony vandalism, according to police.

He was taken to county jail in Richmond and released the following day on bail.

The victim was taken to a hospital to be treated for injuries suffered in the beating and was expected to recover, French said.

The woman told police that her car had run out of gas nearby and that she was looking for assistance when Thompson allegedly attacked her.

Police were unable to locate a second woman who was also reportedly struck by Thompson when she intervened to try to stop the attack, French said.

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