The mistake made was unconscionable.
It seems so, on the surface, but the audio seems to indicate a plausible error in judgement.
I don't own a Taser or a handgun, but I can imagine that if you're well trained, you know which one you're holding at any given time---unless you're in a panicked state, for some reason.
Still, I can't also imagine why this clown thought it was a good idea to try to make a run for it---and that will never be known.