boulder county fire and sheriff's investigators have released the cause of the rabbit mountain fire near hygiene, ruling that it was started by target shooters at round mountain ranch.the boulder county sheriff's office said in a news release that target shooters had been shooting steel plates in the northwest corner of 6303 ute highway when a fragment from one of the rounds ignited nearby grasses, which were extremely dry.`the target shooters attempted to extinguish the fire, but the fire rapidly spread due to the dry fuels on the ground and the weather conditions, including high winds,` cmdr. mike wagner wrote. `the target shooters placed the 911 call reporting the fire.`the rabbit mountain fire burns monday night. investigators say the fire was started by target shooters. (matthew jonas / staff photographer)wagner wrote that investigators are in conversation with the boulder county district attorney's office to determine whether criminal charges will be filed as a result of t...