A Siskiyou County man suffered life-threatening injuries when he crashed an all terrain vehicle without a helmet. At 3:30PM Sunday afternoon 61-year-old Donald Knox was riding an Arctic Cat ATV on Jade Avenue south of Hart Road in the Montague area. He apparently made an unsafe turning motion that caused the ATV to overturn and land upside-down. Knox went flying and sustained major injuries, including to his head as a result of not wearing a helmet. He’s at Rogue Valley Medical Center in critical condition.