A US Iraq veteran was charged Tuesday over the deaths of four homeless people in California, police said, adding that the alleged serial killer had selected more victims before he was arrested.

Itzcoatl Ocampo, 23, of Yorba Linda, was caught on Friday after witnesses chased him from the scene of the fourth fatal attack in Orange County -- of a 64-year-old Vietnam war veteran -- in less than a month.

The first killing on December 20 targeted a 53-year-old homeless man sleeping outside a shopping center, followed eight days later by that of a 42-year-old in Anaheim, in which the victim was stabbed 40 times.

On December 30 a 57-year-old man was stabbed more than 50 times outside a library in Yorba Linda, southeast of Los Angeles, triggering growing alarm that a serial killer was on the loose.

Last week's final victim had been pictured in a story in the Los Angeles Times newspaper, and police believe he was "targeted for participating in this article."

Ocampo "relished the media attention of the crime," said Orange County District Attorney Tony Rackauckas, adding: "We know that he had selected others," without giving further details.

"In each of these cases the violence, the number of stab wounds...

increased," he added, while declining to speculate on a motive and saying he was unaware if Ocampo had been evaluated for psychological problems.

"There are going to be some members of the public who feel less sympathy for these victims because they were homeless and some had criminal records," he told reporters at a briefing to announce the charges against Ocampo.

"Often these types of victims are preyed upon because the perpetrator does not believe that anybody... would miss them. I'm proud to live in a community where we do care about the more vulnerable members of our community." (AFP)