Southern California authorities have warned homeless people in Orange County to be careful if they sleep alone on the streets, following reports that a serial killer, targeting homeless people, has already killed three men.

Orange County Rescue Mission President Jim Palmer said his group is handing out flashlights and whistles to the homeless, in an effort to help them protect themselves, the Associated Press reported. The police have asked homeless people to sleep in groups or in shelters, if possible.

The image of the suspected killer, captured on a surveillance camera, shows a thin man wearing a dark, hooded sweatshirt or sweater, approaching one of his victims lying on the floor.

The body of the first victim, 53-year-old James McGillivray, was found on Dec. 21 near a Placentia shopping mall, while the second victim, 42-year-old Lloyd Middaugh, was found on a riverbed trail in Anaheim a week later. The third victim, 57-year-old Paulus Cornelius Smit, was discovered with fatal stab wounds outside a Yorba Linda library, this week.

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 at a news conference, according to a Los Angeles Times report.

Investigators haven't been able to establish any connections between the victims apart from their homelessness, and declined to reveal further information.