RIVERSIDE, Calif. — A fugitive ex-Los Angeles police officer was charged Monday with murdering a Riverside officer in a potential death penalty case, but hundreds of tips triggered by a $1 million reward failed to end the manhunt.

Christopher Dorner was also charged with the attempted murder of another Riverside officer and two Los Angeles Police Department officers, Riverside County District Attorney Paul Zellerbach said.

The LAPD officers and the Riverside officers were fired on in two separate shootings early Thursday after Dorner, 33, became the target of a manhunt following the killing in Irvine of a former LAPD captain's daughter and her fiance the previous weekend.

"By both his words and conduct, he has made very clear to us that every law enforcement officer in Southern California is in danger of being shot and killed," Zellerbach said at a news conference guarded by four officers armed with rifles.

Authorities obtained a no-bail arrest warrant, which allows Dorner to be apprehended anywhere, Zellerbach said.

Meanwhile, U.S. border inspectors warned that the search for Dorner has created unusually heavy traffic backups at California border crossings into Mexico.

Baja California state police agents were given photographs of Dorner and warned to consider him armed and extremely dangerous.

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Authorities said they were looking into more than 700 tips after offering a $1 million reward for information leading to the arrest of Dorner, who is believed to have written a Facebook rant against those he held responsible for ending his LAPD career five years ago, when a department board determined that he falsely claimed another officer had kicked a suspect.

"Some people are from his past, some people think they saw him yesterday, some think they have information about where he will be," police Lt. Andrew Neiman said.