Itzcoatl Ocampo, 23, was charged on Tuesday with four counts of murder. If convicted, Mr. Ocampo will face a minimum sentence of life in prison and could face the death penalty.
Although the Orange County district attorney, Tony Rackauckas, would not say whether he planned to pursue capital punishment, at a news conference Tuesday, he called Mr. Ocampo “a vicious killer” and offered grim details of crimes that he said grew more brazen and more violent as the killing spree went on.
“The defendant planned the murders in advance, stalked his victims looking for the right opportunity to execute them,” Mr. Rackauckas said. “He had additional victims already selected.”
Mr. Ocampo, who was honorably discharged from the Marine Corps in 2010, stabbed the first victim more then 40 times on Dec. 20, starting while the victim was asleep on the street, Mr. Rackauckas said. The second victim was stabbed more than 50 times on Dec. 27. The third was stabbed more than 60 times on Dec. 30.
Neither Mr. Rackauckas nor the police would speculate about possible motives for the first three murders. By the time of the fourth murder, on Friday, news of a possible serial killer targeting homeless men dominated media coverage in Orange County, and multiple law enforcement agencies had assigned hundreds of officers to the case.
John Berry, 64, a homeless Vietnam War veteran who had slept by the riverbed in Anaheim for years, was pictured in a Los Angeles Times article about the killings. That picture, Mr. Rackauckas said, led Mr. Ocampo to make a target of him.
“The defendant specifically sought this victim out for participating in this article,” Mr. Rackauckas said.
On Thursday, Mr. Berry contacted the Anaheim police to say he thought he was being stalked. They encouraged him to go to a shelter, or to accept some kind of police protection, but he refused, preferring to stay on the street by himself, said Chief John Welter of the Anaheim police.
Then on Friday, Mr. Ocampo passed through both checkpoints that the police had set up to help find the killer. He spoke to officers but did not arouse suspicion. Mr. Berry was killed just after 8 p.m., in a busy shopping center with dozens of witnesses.
After Mr. Berry’s slaying, Mr. Ocampo was chased by civilians into a nearby mobile home park, where he was captured by the police, his face and hands spattered with blood. A large knife, which Mr. Rackauckas said was likely the murder weapon in all four killings, was found nearby.
Mr. Ocampo, who was being held in medical isolation Tuesday, is scheduled to be arraigned Wednesday. His lawyer, Randall T. Longwith, said he did not yet know how his client intended to plead, because neither he nor family members had been able to speak with him.