A brave bystander thwarted an all-too-common crime yesterday, after a thief picked the wrong day to steal a cell phone.

According to the San Francisco Police Department, at 8:58 Wednesday morning a 52-year-old woman riding a Muni bus near the intersection of Geary Boulevard and Laguna Street had her ongoing cell phone conversation rudely interrupted when a 21-year-old man "forcefully grabbed" the device from her hand and fled from the vehicle.

But a Muni-riding good Samaritan was hot on his heels! According to the SFPD, a bystander on the bus saw the incident, then chased the suspect off the vehicle and "pinned [the thief] to the ground until police arrived."

The suspect, SFPD says, was arrested for the strong-arm robbery.