(Portland, OR) -- Portland Police are trying to identify a semi truck that was involved in a fatal crash Friday night in Northeast Portland. Police say 59-year-old Raymond McWilliams was riding his motorized wheelchair on Northeast Vancouver Way near Gertz Road when the wheels went off the sidewalk and he fell under the tires of a passing semi. Police say the driver may not have known he hit McWilliams and didn't stop. McWilliams died at the scene.