A robbery was prevented Thursday by an unusual crime-fighting tool _ a parked car. Karla Gierstors of West Des Moines was walking in downtown Des Moines about 6:15 a.m. Thursday when a man threatened her with a box cutter and grabbed her purse.

A passing motorist stopped to help, and as the robber looked back at the victim he slammed into the car, dropping the purse and box cutter. He then ran away.

Nothing was missing from the purse, but the side and trunk area of the car were damaged.

___

Information from: The Des Moines Register, http://www.desmoinesregister.com