READING, Pa. (AP) — Police say a would-be robber in Pennsylvania had some poor timing when he pulled a gun on his taxi driver with a sheriff's deputy behind him.

The Berks County deputy approached the cab after it failed to move through a green light Monday in Reading.

Surveillance video from inside the cab, obtained by WFMZ-TV , shows the deputy's cruiser pulling up behind the taxi. Shortly after that, the passenger aims a gun at the driver and demands money.

Deputy Terry Ely approaches the cab and asks if there's a problem. Seeing the gun, Ely draws his firearm and orders the passenger out of the taxi.

The cab driver can be heard telling Ely "You're a lifesaver."

Eighteen-year-old Victor Martinez-Herrera was arrested. A lawyer for him wasn't listed in online court documents.