POMONA (CBSLA) — The memorial is growing for a Pomona police officer gunned down in the line of duty.

30-year-old Gregory Casillas died Friday night. The suspect was arrested Saturday after a 15-hour standoff.

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Casillas had only been a Pomona police officer for six months, but he had already made an impact in the community.

Griselda Gonzales said he responded to her 911 call just a few nights ago.

“He came to my home and rescued me and told me everything’s going to be fine,” said Gonzales.

Gonzales said Casillas treated her with kindness, which is why she can’t believe he was the one killed Friday night.

“I’ve been coming here ever since I heard he died that same night,” said Gonzales. “I’ve been coming here. Because I believe that I owe him a lot for being there for me.”

There are still bullet holes and broken glass all around the apartment where 38-year-old Isaias De Jesus Valencia shot at Casillas. And torn walls inside where it looks like he might have tried to escape during the 15-hour barricade afterwards. Some neighbors say they had concerns about Valencia, who police say had an extensive record and had served time for firing a gun in a school zone.

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“We didn’t really know him. The police has been to their apartment many times,” said a neighbor.

But others say the shooting came as a shock to them. That Valencia seemed fine they’d see him around the complex with his family.

“No he was cool,” said neighbor Diana Romann. “Was cool with my sister. His brother was cool. Cool people.”

Police still don’t know why Valencia opened fire. But they’re grateful that Officer Alex Nguyen who was shot in the jaw has now been released from the hospital. And they appreciate everyone in the community coming to pay their respects.

“It’s very inspiring to see the recognition,” said Maria Torres. “And I’m very grateful that the people of this community have responded this way because our police put their life on the line every day.”

Valencia could make his first court appearance as early as tomorrow.

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Officer Casillas leaves behind a wife and two young children. Funeral plans have not been announced yet.