One 19-year-old suspect was in custody at a hospital in critical condition while officers searched for a second suspect, who was identified as 19-year-old Zara Jabbi and was considered armed and dangerous, Toronto police chief Myron Demkiw said at a news conference.
"I urge you to turn yourself in," Demkiw said.
Police officer Marc Pinizotto - who was 43 and had been on the force for 18 years - died of his wounds in a hospital, Demkiw said.
Canadian police had said in March that two individuals emerged from a white Honda RV SUV about 4.30am and fired multiple shots at the consulate building before fleeing.
The shooting damaged the outside of the building but did not cause any injuries.
The consulate attack in March followed heightened tensions over the war launched by the US and Israel against Iran in late February, and it had followed gunfire attacks on two Toronto-area synagogues the previous weekend.
The investigation that led to Pinizotto's death "concerned a number of shootings, including the shooting at the United States consulate on University Avenue. There were several search warrants executed this morning," Demkiw said.
Toronto mayor Olivia Chow said she has known the mother of the deceased officer for the 20 years.
"Their grief is shared across this city," Chow said.
The officer was shot in the early morning in an apartment unit, said Monica Hudon of Ontario's Special Investigations Unit, which investigates incidents involving police officers where there has been a death.
The suspect shot first, Hudon said.
