Miranda Lambert has postponed a concert in Tallahassee, Fla., to attend the funeral of Mark "Tex" Adams, a childhood friend and practice mechanic for motocross racer James Stewart. Her concert, originally scheduled for Friday (Feb. 3), has been rescheduled for May 17. Adams was killed early Thursday morning (Jan. 26) in Florida after he was struck by an SUV while helping a driver who had run out of gas, according to the Florida Highway Patrol. Adams also appeared in the MTV series, Nitro Circus. He was 28.