PATERSON, N.J. — New Jersey’s largest law enforcement union is offering a $10,000 reward for the arrest of the person who shot and killed an off-duty Newark police officer during a robbery in Paterson early Monday.

Public Safety Director Glenn Brown told The Record newspaper the 31-year-old detective walked out of the Sunrise Gentlemen Lounge at about 3 a.m. and was talking to a dancer by his car when they were approached by a man brandishing a gun who demanded money.

Police believe the gunman and the detective may have struggled before the robber fired a shot, striking the detective in his side.

The officer was pronounced dead at St. Joseph’s Regional Medical Center.

Police have not released the name of the officer.

Police are searching for the suspect.