Ontario SWAT officers were called to assist at 1300 W. 5TH Street. The apartments in the area were evacuated and El Camino Elementary School was put on lockdown, according to officials.
Authorities canceled the evacuations and lockdown after discovering the suspect was not inside the apartment building.
Police officers were in a holding position for a while because they had to wait for a search warrant to be issued.
The incident remained under investigation.