The suspect, armed with a knife, approached the child on the 29500 block of Sienna Parkway at about 7:30 p.m. Sunday, according to Orange County sheriff's spokesman Jim Amormino.
The boy was on the swings with another 12-year-old boy when the man approached from behind. One boy ran off while the suspect dragged the other boy about 15 feet away.
The man allegedly told the boy to remove his pants, and then ordered him to remove his boxer shorts. Amormino said at that point, the boy threw some wood chips from the ground into the man's face and fled.
"He did go into the middle of the street, wave down a passing motorist for help," Amormino said.
Amormino said the motorist called 911, but by the time deputies arrived, the suspect was gone.
The suspect was described as a Hispanic man and in his 20s. He was wearing a blue hoodie, blue jeans and sandal, with a bandanna over his face.
Just last week in Whittier, a man attempted to kidnap a boy who was also swinging on a swing set around the same time in the evening. That boy also managed to get away. The suspect was described as having a scar on his right cheek. Deputies are looking into whether the two incidents are related.
Anyone with more information is urged to call the Orange County Crime Stoppers at (855) TIP-OCCS.
City News Service contributed to this report.