YORBA LINDA – Police are investigating a body found outside the Yorba Linda library on Friday, in what appears to be the third killing of a homeless man in Orange County within the past two weeks.

Officers responded to reports of a man down outside the library in the 18100 block of Imperial Highway about 5 p.m., authorities said.

There was blood near the man found lying at the base of a stairwell behind the library, said Sgt. Jim Griffin of the Brea Police Department, which provides police services for Yorba Linda.

The man was unresponsive, and paramedics pronounced him dead at the scene.

While police did not comment on the exact manner of the man’s death, Griffin said trauma on the body leads them to believe it was a homicide.

The library was closing when the body was found, Griffin said. It was reportedly in an area not frequented by library visitors.

Police have not identified the man, believed to have been a transient in his mid-50s.

Brea detectives are reaching out to investigators in Placentia and Anaheim to determine whether the death is related to other recent homicides involving transients.

The first incident took place Dec. 21, when James McGillivray, 53, was found suffering from multiple stab wounds at a retail center in the 100 block of North Bradford Avenue in Placentia.

Surveillance video showed a man with a thin build wearing all black lying in wait before “brutally” stabbing McGillivray, who was known to camp in the area. Authorities described the suspect as an 18- to 25-year-old man, between 5-foot-6 and 5-foot-9.

Less than a week later, on Wednesday, Lloyd Middaugh, 42, was found stabbed to death on the Santa Ana River Trail between Tustin and Lakeview Avenues in Anaheim.

Middaugh was stabbed at least once, Anaheim officials said, and he was pronounced dead at the scene.

A weapon was not found, and authorities have not identified suspects in the stabbing.

No motives have been determined for any of the apparent homicides, and police do not know whether they are linked.

Staff writer Denisse Salazar contributed to this report.

Contact the writer: 714-796-7939 or semery@ocregister.com