The suspect barricaded himself inside a home in the 1900 block of East Cortez Street.
The standoff began after police responding to reports of a loud bang at about 2:49 a.m. and found a casing of a bullet. The bullet had gone through a neighbor's door across the street.
As they searched the area, officers heard another round of gunshots and found another casing. That's when SWAT officers and hostage negotiators were called.
Officials were attempting to make contact with the suspect, calling him over the loud speaker and on the phone.
"We're attempting to make contact, as you can hear with the bull horns in the background, trying to get the resident or the occupant in that house to come out," said West Covina police spokesman Rudy Lopez. "We're uncertain as to who is actually inside the location, but just as a side note, when the officers arrived at the scene, they had also heard live gunfire from the residence so we understand it's a very serious situation."
The last shots heard were fired around 3:20 a.m.
Officers later entered the house where the suspect was believed to have barricaded himself and found the body of a man believed to be the suspect. He was the only person in the house. No shots were fired by police.
Nearby homes were evacuated for safety purposes. Cortez Street between Azusa and Hollenbeck avenues have been closed until further notice.
A motive for the incident has not yet been determined. The suspect's name has not been released.
Anyone with information was urged to contact West Covina police.
The Associated Press contributed to this world.
