(Hood River, OR)  --  Authorities say a bicyclist who was killed in a crash on I-84 near Hood River was a Mosier firefighter.  Police say 52-year-old Ellen Dittebrandt was approaching an off-ramp when she was hit from behind by a pickup truck around 6:30 yesterday morning.  Dillebrandt died at the scene after being thrown off her bike.  The driver of the pickup, 55-year-old John Allman of Portland, is cooperating with the investigation.