It was truly a freak accident, stingrays are very friendly creatures, usually.. they only use their barbs in defense, when they feel threatened or frightened, and getting simply stratched by the barb is EXTREMELY painful, if it pierces in the skin , it causs the boddy to staet shutting down. If it hits the chest, its fatal. In Irwin's case, it pierced his heart, and I bet he died immediately. Stingray venom is among the most potent toxins in the world.. and there's no antidote...