Rear roof rail airbag inflator endcap failure. The endcap of the steel inflator separated and ejected throught the roof liner, read passenger window and through the wall of a house. The vehicle was parked in the driveway at the time and was not running. I was next the the window at the time of failure and was narrowly missed by the end cap but was his by the full force of the passenger window and sustained minor abrasions and closed head trauma from the glass. A police report was filed, and the manufacturer was notified. The vehicle is currently at a dealership awaiting inspection by the manufacturer.