Was this actually an accident by Criss Angel?

I rarely watch Criss Angel but today I watched an episode which I believe is in season 5 (or 4). Apparently they nearly chopped a guys head off with a guillotine (it showed that it went about halfway through his neck). It almost made me sick, but was it a real accident or was it fake? Criss Angel kept yelling for someone to call an ambulance and then I turned it off, I'm not too good with blood :S