Following surgery on Saturday, the other officer involved is expected to recover from injuries sustained in the shooting. Officials didn't identify that officer, but McDonnell said he was shot in the face when he attempted to aid Casillas.
"It's a sad day for the Pomona Police Department, and it's a sad day for our community, and its a sad day for law enforcement in general", said Pomona PD Chief, Michael Olivieri, Jr.in a grim press conference where he announced that one of his officers had died.
Gov. Jerry Brown ordered flags at the Capitol to fly at half-staff and said Casillas' "brave sacrifice will never be forgotten". He was being held on $1 million bail, according to Los Angeles County Sheriff's records.
"However, the suspect failed to yield, and a vehicle pursuit ensued".
The man, identified by police as Isaias De Jesus Valencia, 39, fled on foot and the two officers chased him, the paper reported.
The gunman allegedly led officers to a nearby apartment complex where he was cornered in a unit and began firing his weapon through the door.
The man was holed up in the apartment for more than 15 hours as a SWAT team used flash-bang grenades and cameras to watch him and crisis negotiators tried to coax him into coming out peacefully.
On Sunday, sheriff's department officials said the scene is still being processed and that they could not give a time frame for when displaced residents will be allowed to return. He joined the department in 2014 and worked at several jobs before becoming an officer.
After Casillas' death, colleagues expressed gratitude for the widespread condolences.
The standoff was still ongoing as Saturday afternoon, with authorities saying they did not yet know the suspect's identity nor did they have a motive. "Our hearts are heavy as we mourn the loss of our brother". The child's 27-year-old mother was charged with endangering the welfare of a child. Officer Christopher Ryan Morton, 30, was killed after being dispatched to the wrong house, the Missouri Highway Patrol said.