Decide to try out an unfamiliar tool without assistance
You approach the shiny machine, give it a once over. You don't know what the tool does or how it works, but it doesn't seem too dangerous. You locate the on switch and decide to try it out. The machine fires up with a whirring sound, but you hadn't been paying attention to wear your other hand was and your long sleeve shirt gets caught in the machine's rotating mechanism, catching your arm and mangling it horribly. The sight of all the blood forces you to pass out and you wake up some time later in the ER.