Fake handshake

It's a quite common trap - extending the arm as to give you a handshake. Then the perpetrator may grab your hand and attack you.

Story:
A white male suspect in his mid-50s tried to pull a victim into his car around noon on Oct. 17, UCSF police report.

The UCSF employee, was walking on Judah Street when he heard a man in a passing vehicle honking his horn. The car stopped and the driver asked, “Don’t I know you from somewhere?” while extending his hand as if to greet the victim with a handshake.

The victim then extended his hand to shake hands, at which time the suspect attempted to pull him into his vehicle. The victim was able to strike the suspect with his free hand and pull away from the suspect.

Source