(CNN) -- Authorities on Sunday identified a man arrested in connection with a series of fatal attacks on homeless men in Southern California.
Itzcoatl Ocampo, 23, of Yorba Linda, California, was apprehended Friday night after he allegedly stabbed a transient to death in Orange County, said Anaheim, California, police Sgt. Bob Dunn on Sunday.
Witnesses told police they had seen a man stabbing a homeless man, Dunn said. Several witnesses chased the suspect after he fled on foot, he said.
When officers arrived, witnesses directed them to the last place the suspect was seen, and he was detained without incident, Dunn said. The victim's name was not released.
Ocampo is facing charges in the murders of four homeless men, Dunn said.
Dunn would not comment on a Los Angeles Times report Saturday that cited Ocampo's family members as saying he was a former Marine who experienced difficulties after returning from Iraq.
Authorities have been searching for a serial killer after three homeless men were stabbed to death over 10 days last month in Anaheim, Brea and Placentia.
The three men were "stabbed multiple times," Dunn said. "There are some additional similarities between the victims that we are not going to discuss."
The first victim -- a 53-year-old male -- was stabbed on December 20 in Placentia. Eight days later, a 42-year-old man was found fatally stabbed on a riverbed trail in Anaheim. A third victim, 57, was found on December 30 in Yorba Linda.
Police had released a surveillance camera photo of the suspect taken from December 20. It shows the suspect standing a few feet away from the victim, who appears to be lying on the ground next to a strip mall, according to police.
Investigators urged the homeless to stay in groups and avoid sleeping in dark and secluded areas.
Authorities set up a task force to probe the killings, which includes the FBI and the Orange County Sheriff's Department.
News of the arrest came as a relief, said Sue Siegel of Mary's Kitchen, an organization serving hot meals to Orange County's homeless.
"I said, 'Thank God, these guys can try and get some good sleep and try not to worry,'" she said. "But on the streets it's hard to get good sleep anyway."
She said the slayings had the homeless on edge.
"They were kind of not relaxed like they usually are," she said. "They were doing the buddy system while they were sleeping at night. They were buddying up -- one would watch while the other slept, watching each other's backs -- which they never used to do."
CNN's Irving Last contributed to this report.