Two people opened fire at police officers near a grocery store in Jersey, New Jersey, local police sources said.
According to the Hudson County Prosecutor's Office, at least one of the police officers was killed and three others were injured - two more officers and a civilian. The condition of the victims is stable.
Witnesses say the gunfire lasted for at least an hour. All schools in the city are closed and all students are safe, authorities said. The Emergency Management Service called on people to avoid the area.
In Washington, White House spokesman Hogan Gidley said President Donald Trump has been informed and is monitoring the situation.
The suspects are reported to be man and woman. It is still unclear what their motives were. Police sources say the incident did not have any terrorist instigation, according to initial reports.