Police say a gunman who killed his young son and injured his wife and other son in northern New Jersey was separated from his wife and had a restraining order issued against him.

Paterson Police Detective Lt. Ronald Humphrey had no details Sunday on why the restraining order was issued against Edelmiro Gonzalez, but says the couple separated earlier this year. He says investigators are still searching for a motive in Saturday's shootings.

Gonzalez was shot and killed by an off-duty Paterson police officer, Lt. Washington Griffin.

Gonzalez's 7-year-old son was killed. His wife and 11-year-old son remain hospitalized in critical but stable condition.

Humphrey says Griffin was placed on administrative leave pending an investigation, a standard procedure in police-involved shootings.