ANCHORAGE, Alaska (AP) — A gay pride parade in downtown Anchorage, Alaska, has been canceled after a convertible carrying the grand marshal fatally struck a man.Anchorage police Lt. Dave Parker says the 50-year-old man who was killed was participating in the celebration.Parker says the accident happened just minutes after the parade started Saturday morning when the car accelerated and ran over the man. He died at the scene.Police have questioned the driver and authorities are trying to determine whether the collision was caused by mechanical or driver error.Grand marshal Doug Frank told the Anchorage Daily News that the driver of the vehicle had trouble with the car's accelerator.