The incident happened around 2:30 p.m. Tuesday on the 500 block of 6th Street.
Deputies said the boy, whose age was not released, was able to get away from the suspect. The man fled the scene before deputies arrived.
Investigators later tracked down the suspect, 42-year-old Marcos Carrillo of Norco. Deputies said based upon the suspect's demeanor and actions, he seemed "to be motivated by an abnormal interest" in the victim.
Carrillo was arrested for annoying and molesting a child.