A 33-year-old man from Biggs Junction was killed early Monday evening when he was fatally struck by a commercial truck while walking on Interstate 84 near milepost 104 in Sherman County.  According to the Oregon State Police, the truck was traveling westbound on Interstate 84 in the slow lane at about 5:45 p.m. on Monday when the driver noticed a reflective vest moving around in the lane of travel.  The OSP says the driver initially thought the vest was blowing around in the wind, but then realized it was being worn by a pedestrian.  The truck swerved to avoid the person, but was unable to avoid striking him.  The pedestrian, Alejandro Lozano Rivas, was pronounced dead at the scene.  The OSP says the driver, a 31-year-old man from Moscow Mills, Missouri, stopped immediately at the scene and is cooperating with investigators.