Investigators from the San Francisco Police Department are poring over Muni surveillance video after a passenger was attacked and robbed of his dog.

The 18-year-old victim was on a Muni bus traveling on Mission Street near San Francisco's infamous Sixth Street a 2:38 a.m. Thursday when the attack and theft occurred.

According to San Francisco Police Department spokesperson Officer Grace Gatpandan, a man, described only as "in his 20s," got on the bus, then approached the teen and punched him in the face.

After the assault, the man dragged the victim's dog from the backpack in which the pup was being carried, and ran back off the bus, witnesses say.

Gatpandan says that police have pulled the surveillance video from the Muni bus, and are hopeful it can be used to identify the violent dognapper. So far, however, no arrests have been made.