An Oak Harbor man is facing a felony charge for allegedly hitting his 83-year-old grandfather hard enough to break his skull in three places, court documents state.

William A. Allman, 30, pleaded not guilty in Island County Superior Court May 28 to assault in the second degree, a domestic violence crime with aggravating circumstances.

The aggravating circumstance, court documents state, is that the victim was particularly vulnerable.

If convicted of the charge, Allman could face up to a year and two months in prison under the standard sentencing range.

Oak Harbor Police Officer Patrick Horn said he responded to the report of an assault on Northeast Fourth Avenue on May 15.

The conflict started after Allman’s grandmother refused to let him use her car. He started arguing with her, so her husband intervened.

Allman allegedly punched his grandfather once on the side of the face, then left.

Horn wrote that the victim’s face was clearly bruised and that he was groggy and dizzy.

Paramedics transported him to Whidbey General Hospital for treatment.

Doctors discovered the man suffered fractures in three parts of his skull. He was transferred to Harborview Medical Center and Hospital in Seattle for further treatment.