California police believe a serial killer is stalking the homeless in Orange County, warning those who can to seek shelter at night.

The New York Times reported that the demand for beds at some shelters was up as much as 40 percent in the last couple of days after the separate stabbing murders of three homeless men.

Police have described the attacker as a thin man between the ages of 18 and 25.

"We believe these murders are likely committed by the same suspect and we feel he is extremely dangerous to the public," Anaheim police Chief John Welter told reporters, according to Reuters.

The three killings all took place in the last two weeks of December, most recently on Dec. 30, when a 57-year-old homeless man was found stabbed at the bottom of a stairwell outside a library in Yorba Linda, police said.

Also killed were a 42-year-old man, whose body was found by someone on a bike trail in Anaheim, and a 53-year-old man found stabbed to death at a shopping center in the city of Placentia.

The Orange County Rescue Mission was handing out flashlights and whistles to the homeless to help them protect themselves, group president Jim Palmer said, according to the Associated Press.

“People are very, very anxious about the situation,” Palmer said, the Times reported. “This is just so evil that somebody would go after the least, the last and the lost of our community: homeless people on their own.”