Investigators believe a serial killer was responsible for the slayings of three middle-aged homeless men who were stabbed to death last month. No possible motive has been disclosed.

The body of the first victim, James McGillivray, a 53-year-old man, was found December 21 near a Placentia shopping mall. The second victim, Lloyd Middaugh, a 42-year-old man, was found on a riverbed trail in Anaheim a week later. The third victim, Paulus Smit, who was 57, was discovered with fatal stab wounds outside a Yorba Linda library. Police have been warning homeless people throughout Orange County not to camp or sleep in secluded areas.

“We believe these murders were likely committed by the same suspect and feel he is extremely dangerous to the public,” Anaheim Police Chief John Welter said.

Police have been reviewing surveillance video from the scene of the first murder. The authorities released photos from the security footage that they hope will lead to the killer and a possible witness. Police say they believe a 2000-2003 model white four-door Toyota Corolla captured in the surveillance video could belong to the suspect or a witness, who police still want to speak with. Police obtained a photograph of a possible suspect from the same video as he approached the victim, later identified as James Patrick McGillivray, 53. The suspect is wearing a dark, hooded sweat shirt or sweater. Authorities asked for the public’s help in finding the killer.

Police are beefing up their patrols throughout north Orange County as a result of the killings. Authorities have formed a task force involving Anaheim, Brea and Placentia police departments.

“At this time we have not ruled out the possibility that there is one or more suspects, but all of those things are still under investigation,” said Anaheim Police Sgt. Bob Dunn.

If you have information related to these murder cases, contact the Anaheim Police Department at (714) 765-1944.

-articles from CBS.news and ABC Local rewritten and adapted by admin-