A.J. Pero was a very talented drummer. He wasn't underrated, but he was certainly overlooked. It sucks that this happened, but the cause of death doesn't surprise me much. More people should pay attention to their bodies and get themselves checked out periodically, especially if they can afford medical care. Fifty years of age is nothing. Wait until you've hit your ninth decade.
My favorite releases with him are Twisted Sister's Under the Blade and Cities' Annihilation Absolute. I've always been able to and still can go back to those albums. It's a shame that Cities never made another album. What great potential this USPM band had.