SANTA ANA, Calif. — A 23-year-old former marine who some say was distraught following combat service in Iraq has been named a suspect in the serial killings of four homeless men in Orange County.

Itzcoatl Ocampo, of Yorba Linda, was chased bystanders Friday following the most recent stabbing death in the parking lot of an Anaheim fast food restaurant. On Saturday, Ocampo remained in police custody without bail and is expected in court on Tuesday.

“We are extremely confident that we have the man who is responsible for the murders of all four homeless men in Orange County,” Anaheim Police Chief John Welter said at a news conference Saturday. Police said they will seek four counts of murder next week.

Authorities did not specify a motive for the killings, which began on Dec. 20 and sent fear through the homeless community. However, a relative and a friend of the suspect described a young man who appeared to be deeply troubled following his return from service in Iraq in the summer of 2010.

“When he came back from Iraq he was sick,” said his uncle, Ifrain Gonzalez.

For the last year, he had been telling relatives that he was seeing and hearing things, Gonzalez said.

The last time Gonzalez saw his nephew was at a Dec. 24 Christmas Eve party. Ocampo, he said, had told a cousin: “I did something terrible, but don’t worry.”

It was four days after the killings had begun.