WHITTIER (AP) — Several good Samaritans chased down and detained a registered sex offender who allegedly tried to kidnap an 18-year-old woman, Southern California authorities said.

David Polanco, 41, was booked by Whittier police for investigation of kidnapping and held in lieu of $100,500 bail, the Los Angeles Times reported (http://lat.ms/XYi4qP ).

Polanco convinced the woman to walk around with him for a few hours in Whittier on Wednesday, and then allegedly tried to grab her around the waist from behind and pull her into an alley, police said.

Polanco fled after witnesses saw the two struggling and called 911, police said.

A group of men sitting at a nearby cafe chased the suspect and held him until police arrived and arrested him.

Investigators said Thursday that Polanco is not believed to have been involved in a series of recent kidnapping attempts in Whittier.

A photo lineup was compiled with Polanco's mugshot and shown to the earlier victims, who didn't recognize him as their attacker.

On Tuesday, a 12-year-old boy told police he was playing in Parnell Park in Whittier when a man tried to pull him off a swing set. The boy and his brothers fought off the suspect and the man ran away. Police are seeking a red convertible in connection to that case.

Last month an 11-year-old girl walking alone near Founders Park was grabbed by a man and shoved into the back seat of a car where a sobbing 7-year-old was already being held, investigators said.

The older girl managed to get out of the car and free the 7-year-old, and both girls ran in different directions to escape the suspect, Officer Brad White said. Police believe the suspect in the girls' case to be a different person from the Parnell Park suspect.