(Cornelius, OR) -- Police are looking for witnesses after a someone riding a motorized scooter crashed into and killed a pedestrian last week. The Washington County Sheriff's Office says 51-year-old Tammera Whisman of Hillsboro was walking near 2240 Baseline Street last Tuesday afternoon when the scooter struck her. She died at the scene. Police say the person riding the scooter stayed at the scene and is cooperating with investigators. No charges have been filed. Police are asking anyone who witnessed the collision to contact them.