LOWELL — An off-duty sergeant with the Middlesex Sheriff’s Office is facing charges in what is described as a road-rage incident. William G. McLean is accused of stopping a driver, frisking him and then punching the driver when he asked for identification.

In Lowell District Court on Monday, McLean, 54, of 19 Franklin St., Billerica, was released on personal recognizance after pleading not guilty to operating under the influence of alcohol, assault and battery, and lights violation.

McLean has been suspended with pay pending the outcome of an internal investigation, according to Kevin Maccioli, public-information officer for Middlesex Sheriff Peter Koutoujian.

Lowell police arrested McLean around 5:40 p.m. on Friday after receiving a report of an alleged road-rage incident that began when the alleged victim, who was driving with his girlfriend and two children in the car, reported a man in a car behind him kept flashing his lights and following close behind his car. Both cars pulled into a store parking lot on Plain Street where the drivers exited their vehicles.

McLean allegedly told the victim he was a state police trooper, carrying a police-style radio with “MSO” on it and a high-powered flashlight. McLean allegedly told the victim to place his hands on his car while he pat-frisked him. When the man asked McLean for some police identification, he said McLean punched him, according to court documents. The man struck back and McLean allegedly chased the victim around his vehicle until some passers-by intervened, according to documents.

When police spoke to McLean, he allegedly told officers he was jumped by several people in the parking lot. Police reported they could smell alcohol on McLean’s breath. When McLean was asked how much he had to drink, he allegedly admitted drinking a few beers.

Police allege McLean failed field-sobriety tests. McLean allegedly registered a .11 on a Breathalyzer test, which is more than the legal limit of .08.

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