Apparently, some kinds of cocaine use result in overheating, so the perps strip down. The cannibalism is an oddity, and if he took multiple shots while still eating, I'm not ruling out George Romero's involvement.
I found another version of this story and it's said the drug was LSD. I wonder what Timothy Leary would think about his wonder drug.
"Any Government Big Enough To Give You Everything You Want Is Also Big Enough To Take Everything You Have."-Thomas Jefferson