Seven-year-old Adrian Gonzales was pronounced dead at the scene, while his 11-year-old brother, Edryn Gonzales, and their mother, Johanna, 31, were both hospitalized in critical condition. Humphrey would not disclose further details on their injuries.
The gunman, Edelmiro Gonzales, 54, was also taken to the hospital, where he died a short time later.
Shortly after the shooting, police cordoned off two blocks in the area and recovered some shell casings, but it was not immediately known what type of weapon was used.
Humphrey would not release any additional information, including the identity and work status of the officer who shot Gonzales, saying the investigation was ongoing.
Will Hayes, a city resident who witnessed the shooting, told The Record of Bergen County that the gunman ran after the three victims and fired "multiple shots." He said the off-duty officer -- who was in a car at a nearby fast food restaurant -- saw what was happening and confronted the man, telling him to stop and drop his weapon.
When the gunman refused the order, the officer shot him, Hayes said.
"One kid was trying to get up," Hayes said. "They were young. I started crying."