Authorities have identified a man arrested Saturday, accused of shooting two police officers in Pomona, Calif., killing one of them.

Isaias De Jesus Valencia, 39, was apprehended Saturday after barricading himself in an apartment and holding a SWAT team at bay for more than 15 hours, authorities said.

Police had tried to stop the suspect Friday night after receiving a call about reckless driving, but he refused to pull over and led officers on a pursuit, Los Angeles County sheriff's officials said.

The man crashed during the chase and fled into an apartment complex.

Officers pursued the suspect, who fired through the door, shooting one of the officers, Los Angeles Sheriff Jim McDonnell said.

A second officer tried to rescue his wounded comrade and the gunman fired through the door again, striking the officer in the face, the sheriff said.

Pomona Police Officer Greggory Casillas, 30, of Upland, was killed. The other officer was undergoing surgery Saturday and was expected to recover, officials said.

"He left his family at home to protect yours and his ultimate sacrifice will never be forgotten," Pomona police Chief Michael Olivieri said at a news conference.

Casillas first joined the police department in Pomona, which is 30 miles east of Los Angeles, as a records specialist in 2014. He then worked as a jailer and became a sworn police officer in September. Casillas was finishing his field training when he was killed Friday night, KTLA reported.

He leaves behind a wife and two small children.

Pamona Police Department tweeted Saturday night: “We are deeply moved by the love and support we have received from our law enforcement brothers and sisters, our community and people across the US during this difficult time. Our hearts are heavy as we mourn the loss of our brother, Officer Gregg Casillas.”

Gov. Jerry Brown ordered flags at the Capitol to fly at half-staff and said Casillas' "brave sacrifice will never be forgotten."

Outside the Los Angeles County coroner's office, dozens of police cars lined the streets and officers saluted as the slain officer's body was brought there in a procession Saturday.

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.

The man was taken into custody without bail and led out of the building wearing only his underpants.

McDonnell said that it had been "a long night" but now that the scene was secure and safe, officials could begin their investigation.

During an afternoon news conference, Olivieri said it was "a sad day" for the Pomona Police Department, community and "law enforcement in general."

"Our Pomona officers were out doing what they always do - putting themselves in harm's way to protect Pomona, a community that we love," he said.

The Los Angeles Times reported the suspect was contained in the apartment and around 7 a.m., local time, a "loud bang was heard." An officer was heard instructing the suspect to come outside the apartment with their hands up.

OFFICERS KILLED IN THE LINE OF DUTY IN 2018

Video footage from local media showed exchanges of gunfire while a wounded officer was on the pavement, receiving medical attention.

At least 21 police officers have died in the line of duty since the start of 2018.

The Associated Press contributed to this report.