Story highlights Joseph Walker, a New Jersey detective, is charged with second-degree murder

Maryland State Police say he fatally shot driver Joseph Harvey Jr., after an altercation

Walker's wife, kids were with him during the apparent road-rage incident, police say

A New Jersey law enforcement officer is charged with murder after police say he shot a man in an apparent road rage incident in Maryland, according to authorities.

Joseph Walker, a sworn officer of the Hudson County prosecutor's office, is accused of fatally shooting a motorist Saturday during an altercation off of Maryland's Route 3.

The preliminary investigation suggests that two vehicles came to a stop on an exit ramp after a previous altercation. One of the drivers, Joseph Harvey Jr., and a passenger then exited their vehicle and walked toward Walker's, according to a news release from Maryland State Police.

Walker, 40, allegedly fired a .45 caliber Glock at Harvey and struck him. Harvey, 36, died of his wounds Saturday night at Baltimore Washington Medical Center.

Elena Russo, spokeswoman for the Maryland State Police, told CNN affiliate WJZ that Walker's wife and three children were in his vehicle at the time of the shooting.

Hudson County prosecutor's office spokesman Gene Rubino says his office is aware of the fatal shooting involving one of its detectives, who was off-duty and traveling in Maryland with his wife and children. Rubino refused to comment further.

It is unclear whether Walker has an attorney.

Walker is facing second-degree murder and manslaughter charges. He is being held on a $1 million bond, Maryland State Police said.