Police say a masturbating bus passenger threatened a mother with a knife on board a Bronx bus when she asked him to stop fondling himself.

The 27-year-old woman was on board the BX2 bus with her children in Morris Heights on July 9 when she observed the man masturbating, police said. She asked him to stop and alerted the bus driver. 

The suspect approached the woman and brandished a knife, according to police. The two struggled and the victim grabbed his hand to defend herself.

The suspect ran off the bus as it stopped at East 171st Street and Grand Concourse. No one was hurt.

Anyone with information is asked to contact Crime Stoppers at 800-577-TIPS.