A light piston twin accident nearby, 30 years ago, was found to be fueled with Jet-A rather than 100LL.
Yes, pilot negligence, because he had signed the fuel receipt stating clearly "Jet-A".
And the lineboy had seen the "Turbo" logo on the nacelles (i.e. turbosupercharged) so he was confident he had selected the right fuel.
Neither the first nor last time, unfortunately.