Police later accused Shaquan Johnson, 27, of Newark of shooting the police officer, and authorities were investigating his possible involvement in the other two shootings.
The gunman first drove up to a vehicle stopped at a traffic light, according to a police news release. He spoke with the driver, a 23-year-old man from Bridgeport, Conn., before shooting him several times.
The gunman continued driving and shot to death Gary Farrar Jr., 22, a Rutgers University student walking on a sidewalk, police said.
A man then passed an Irvington police patrol car, backed up and told the sergeant inside, a 24-year police veteran, that a shooting had just taken place, police said. He then drew his gun and shot the sergeant.
The Connecticut man drove himself to a hospital in Newark, and an ambulance took the sergeant to a hospital. The sergeant was treated and released.
Law enforcers stopped a sport utility vehicle that Johnson was driving at about 9:30 a.m. The vehicle was similar to the one witnesses saw leaving the scene of the officer's shooting, Loriquet said.
Johnson was initially was arrested on drug possession charges but later charged with aggravated assault on a police officer, two weapons offenses and possession of hollow point bullets.
He was being held Sunday night in jail on $500,000 bail. Loriquet didn't know whether Johnson had a lawyer.