Since Dec. 21, three Orange County, Calif., homeless men have been stabbed to death. Local authorities are trying to find out if someone is targeting the region’s homeless and are asking residents to look out for their indigent neighbors. According to the City News Service, the first killing occurred Dec. 21 outside a shopping center in Placentia. James McGillivray, 53, was found with multiple stab wounds. Video from near the scene showed a thin man, wearing all black, lying in wait before the attack, police said. Eight days later, a 42-year-old man was found stabbed to death along a riverbed trail in Anaheim, according to police. Then, two days after that, on Dec 31, a 57-year-old man was found stabbed to death in Yorba Linda, in a stairwell just outside a library. The Yorba Linda victim was identified Saturday as Paulus Cornelius Smit, whose last known address was in the city, The Orange County Register reported. Detectives have not established whether one person committed all three killings. “We want everyone to watch out for the homeless population,’’ Dunn said. “If they see something unusual, give us a shout.”