JERSEY CITY -- The off-duty Jersey City police officer who shot and killed a man in East Orange on Saturday afternoon has been involved in at least two other fatal shootings since 1999.

Numerous law-enforcement sources have identified Titus Johnson, a Jersey City police sergeant, as the officer involved in Saturday's deadly incident. Johnson, who owns a home on the East Orange street where the shooting occurred, has been on Jersey City's police force for 24 years.

He shot and killed a stabbing suspect in December 1999 while off duty but in uniform and in 2004 shot and killed a man during a traffic stop. He also shot and wounded a man during a 2004 foot pursuit.

Essex County prosecutors, who are investigating Saturday's incident, said in a statement today that the officer shot Samir Nicholson, 24, of East Orange, after Nicholson shot a third, unidentified male (that person was treated and released from University Hospital). Eyewitness News reported that one witness called Johnson a hero, saying he saved her brother's life.

Johnson could not be reached to comment, but his union defended him in a statement to The Jersey Journal.

"Our officer was forced to make a decision no one in law enforcement ever wants to, but is well trained to," said Robert Kearns, president of the Jersey City Police Superior Officers Association. "As the investigation progresses we are confident it will show that his actions made others safer."

Jersey City spokeswoman Jennifer Morrill declined to comment, saying Essex County is handling the investigation.

In 2005, Edward DeFazio, then the Hudson County prosecutor, said Johnson's involvement in three shootings was "extraordinary," adding that the vast majority of Jersey City cops will never shoot anyone.

Tom Aveni, executive director of New Hampshire-based Police Policy Studies Council, which provides forensic consultation to police departments and conducts behavioral research, told The Jersey Journal that Johnson's involvement in three fatal shootings is unusual, but he needed more context to reach a conclusion about Johnson's actions.

"If you're working in a particularly violent city and you're making a lot of felony arrests for robbery, sexual assault ... an officer making a lot of arrests can use force disproportionately simply because of the arrests he's making," he said. "If he's not making arrests, it would be a red flag."

Johnson has received 13 awards and commendations throughout his career, city records show.

On Dec. 17, 1999, Johnson stopped on his drive to work when he saw a fight on Mercer Street near Summit Avenue, authorities said at the time. One of the men, 19-year-old Nelson Vasquez, had already stabbed his victim twice and was about to stab him again when Johnson fired one shot from his service weapon, striking Vasquez in the back, authorities said. Vasquez died from his injury that night. The next year Johnson received a commendation at the Hudson County Valor Awards.

Five years later, in September 2004, Johnson shot a man in the leg after the man allegedly aimed a gun at officers during a police chase.

On Dec. 30, 2004, Johnson shot and killed 49-year-old Raymond Looney during a traffic stop at Newark Avenue and Coles Street. A Hudson County grand jury decided to take no action against Johnson, who said Looney tried to drive away as Johnson approached the car, clipping the officer in the process. Johnson opened fire, hitting the man twice, once in the side and once in the back.

Johnson is also at the center of a lawsuit targeting Jersey City's police force (he is not a defendant). The mother of a three-month-old boy killed on July 27, 2012 by the boy's father alleges Johnson had the chance to arrest the man one day prior and didn't. That civil case is headed to trial on June 26.

In 2009, Johnson received $150,000 from the city to settle a lawsuit he filed alleging workplace discrimination.

Terrence T. McDonald may be reached at tmcdonald@jjournal.com. Follow him on Twitter @terrencemcd. Find The Jersey Journal on Facebook.