SANTA ANA, Calif. — The Iraq War veteran would carefully stalk each of his victims from among the thousands of homeless living in Southern California. He would then stab them repeatedly with a knife that could cut through bone, authorities say.

For his fourth and latest victim, they say, Itzcoatl Ocampo selected a homeless man featured in a Los Angeles Times story about a killing spree that terrorized those living on the streets for weeks.

And Ocampo had plans for more, until he was chased down by bystanders Friday night after the fatal stabbing of a 64-year-old homeless man. He was caught with blood on his hands and face, authorities say.

"He was a monster," Orange County District Attorney Tony Rackauckas told reporters at a news conference. "He was a terrible threat, particularly to the homeless people in our community."

Ocampo was charged Tuesday with four counts of murder and special allegations of multiple murders and lying in wait and use of a deadly weapon. Three victims were stabbed more than 40 times each with a single-edged blade at least 7-inches long.

Authorities declined to say whether they had identified a motive. Rackauckas said he had no indication that Ocampo was mentally ill.

Ocampo's family said the 23-year-old was a troubled man after he returned from Iraq in 2008. Ocampo was being held in isolation at an Orange County jail while officers keep an eye on him 24 hours a day, officials said.

If convicted, Ocampo faces a minimum sentence of life in prison without parole. Authorities have yet to decide whether to seek the death penalty.

Ocampo is due to appear in court on Wednesday, but his attorney said his arraignment would likely be postponed since the attorney was not allowed inside the jail to speak with his client over the weekend and has met with him only briefly.