The California Department of Corrections says that 39-year-old Isaias Valencia was committed to state prison in 2014 with a two-year sentence for possession of a firearm and ammunition, discharging a firearm in a school zone and destruction of jail property.
Police said Valencia led them on a short chase Friday night before barricading himself inside his apartment. Valencia then fired multiple shots, killing 30-year-old Officer Gregg Casillas and injuring Officer Alex Nguyen, investigators said.
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Valencia was arrested on Saturday after a 15-hour standoff. Authorities said he was booked on suspicion of murder of a police officer and attempted murder of other peace officers.
A view from inside the apartment shows Valencia blasted holes in the walls with his gun in an apparent attempt to escape through a neighboring unit.
Lucero Torres was frightened for family members who were in that adjacent apartment.
"Kind of scared. I thought I was gonna lose them," Torres said. "Because they were next door to the guy. He was trying to make a hole to go to my house. The bedroom mirror is shattered because it went through the walls."
Residents of the neighborhood where the standoff occurred were still shaken up on Monday.
Pomona Mayor Tim Sandoval visited the area to talk to residents: "We're all mourning," Sandoval said. "We lost an officer. We had an officer that was wounded, who is recovering. And then we had a community of people who had to experience this."
Diana Roman, who lives in the unit below Valencia's apartment, said he lived there with his family, who she described as outgoing and friendly.
"Sometimes drugs take over, like he did have a mental illness. I'm not saying it's OK, you know, but he was on drugs and he was drunk...you never think s--- like that's going to happen or your neighbors are capable of things like that," Roman said.
Pomona resident Arlene Sepulveda paid her respects at a growing memorial for Casillas at the Pomona Police Station, leaving a candle and a donation for his wife and two young children.
"It really struck hard for the city of Pomona...my kids, they grew up in this city. They see the news, and they were just devastated - they were like - how can it be so close to us?" Sepulveda said.
Hundreds of people gathered Sunday night for a vigil honoring Casillas.
Pomona police said Monday that Nguyen has been released from the hospital and is doing well. An autopsy for Casillas was scheduled for Monday.
Valencia is due in court for the first time on Tuesday.