GAMBRILLS, Md. — A New Jersey police detective who was traveling with his wife and three young children has been charged with second-degree murder after a road rage incident ended in gunfire along a Maryland highway on Saturday, authorities said Sunday.

Joseph Walker, 40, a detective with the Hudson County Prosecutor’s Office, is accused of shooting a 36-year-old Maryland man on the shoulder of a ramp leading to Route 97 in Gambrills, a Baltimore suburb, according to the State Police there.

He is also charged with manslaughter.

Walker, who lives in Eastampton Township, near Mount Holly, was being held Sunday at the Anne Arundel County Detention Center on a $1 million bond. He works for the Hudson County Prosecutor’s Office and has been a public employee for 17 years, according to state pension records.

"We are aware of the fatal shooting incident involving one of our detectives, who was off duty and traveling in Maryland with his wife and children," Gene Rubino, spokesman for the Hudson County Prosecutor’s Office, said in a statement. Rubino declined further comment.

Officials in Maryland said Sunday they were still trying to piece together what happened along the busy highway as the sun set Saturday.

It appeared, State Police said, the incident started because of road rage that began brewing on Route 3, about a mile from the shooting. Walker was traveling in a gold Kia minivan with his family — including his children, ages 3 through 11 — when he encountered Joseph Harvey Jr, a Halethorpe, Md., resident, who was driving a green Honda Accord and riding with one passenger, authorities said.

For some reason, police said, both men pulled to the side of the road on a northbound ramp to Route 97. Harvey exited his car and began to approach Walker, who also got out of his minivan and, according to a statement from State Police, "allegedly announced that he was a police officer."

"Harvey continued to approach Walker in a reportedly aggressive manner," the police statement continued, noting that the passenger remained by the side of the Honda. "Walker then brandished a firearm and shot in the direction of the two men, injuring Harvey."

Harvey was taken to Baltimore Washington Medical Center, where he was pronounced dead after the 8:30 p.m. shooting, police said.

Walker was also taken to the hospital because of chest pains.

An autopsy revealed that Harvey was shot three times, according to Elena Russo, a spokeswoman for the Maryland State Police.

"None of the wounds showed evidence of being fired at close range," Russo said.

She said she did not know if the .45-caliber Glock pistol Walker used during the shooting was issued by the prosecutor’s office.

Walker appeared before a District Court commissioner Sunday and is scheduled to be in court again today for a bail review hearing.

He was charged by police after consultation with the Anne Arundel County State Attorney’s Office.

Russo said detectives are continuing to investigate witnesses to the shooting, some of whom may not have come forward yet.

"It’s a busy portion of the roadway there," she said. "So there were of lot a motorists going by at the time."

Witnesses are asked to call the Maryland State Police in Glen Burnie at (410) 761-5130.

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