Police are searching for a suspect after a teenager was robbed of his wallet while walking through a Cambridge park.

The boy was walking through St. Andrews Park on his way to a Grand Avenue library Monday afternoon when he was approached by a man.

The man told the boy he had a knife, and demanded the boy turn over his wallet.

The boy gave the man his wallet, then ran home and called police.

No knife was seen.

The suspect is described as white, 18-19 years old with medium-length blonde hair. He was wearing a black parka with fur around the hood and a red baseball cap turned backwards.