The moves come after three homeless men were murdered in separate incidents since Dec. 21 in the north side of the county.
On Friday, the body of a 57-year-old transient was found covered in blood next to the Yorba Linda Library.
On Wednesday, 42-year-old Lloyd Middaugh was found dead with multiple stab wounds along the Santa Ana River trail in Anaheim.
On Dec. 21, 53-year-old James McGillivray was found dead outside a strip mall in Placentia. Police said he was violently stabbed to death where he often slept.
Investigators from Anaheim and Placentia are joining Brea police to see if the three killings are the work of one suspect.
Police are handing out the fliers in places where transients are known to hang out.
"They told us there they consider it a serial killing," said Denny Albertson, who has been homeless for more than five years.
Albertson hangs around the Santa Ana River trail in Anaheim with friends. He said he's been extra cautious since learning about the killings.
"I don't carry weapons, but last night I went home and I thought maybe I should have a weapon in case I'm attacked," he said. "At least I have something right there to grab. I made me a billy club."
Police are hoping residents report suspicious people or activity to prevent further crimes.
Anyone with information that could help investigators is asked to contact Anaheim police at (714) 765-1944.