Two Lancaster residents were killed in a single-vehicle collision on Highway 14 freeway in Canyon Country early Sunday morning. Shortly after midnight, driver Tiesha Shepherd, 37, and her passenger Johnnie Mitchell,48, were traveling northbound in a 2003 GMC SUV at a high rate of speed, according to a California Highway Patrol news release. The SUV slammed into a guardrail and flipped. Shepherd and Mitchell were both ejected onto the road. Los Angeles County Fire Department paramedics pronounced the two crash victims dead about 17 minutes into the call, according to Dispatch Supervisor Bernard Peters. Their causes of death have not yet been determined, according to Rudy Molano with the Los Angeles County Office of Medical Examiner-Coroner.