I was chatting to a friend of the man who had the accident with the matador wheel. His leg was not blown off but broken and the blunt edge of the wheel rim cut about half way through the muscle. He said the bolts were badly wasted between the halves of the rim. All i can suggest is when he was undoing the last of the wheel nuts he failed to notice the rims opening up, mabey he thought the whole wheel was tilting over as he slackened the second from last nut and when he removed the last nut it went tits up.