I'm playing a Pathfinder adventure path as a magus, and the last couple of boss fights have ended with me making critical hits with the spell shocking grasp.
In the first instance, fighting a necromancer, I got a natural 20, confirmed the critical hit, and dealt a boatload of damage (about 60 points of electricity damage plus my weapon's damage). The GM ruled that the boss was vaporized, the boss's equipment destroyed. That was annoying as we wanted to search his equipment for clues, but it was a natural 20, so whatever. The party paladin even lectured me about using excessive force, the irony making everyone chuckle.
Tonight's boss went down to another this-time-not-a-critical-hit shocking grasp that dealt less damage against what I believe to be a higher CR foe. Again the GM ruled that the boss was obliterated and all his stuff destroyed.
Now, I'm aware of Rule Zero, but the GM isn't super familiar with Pathfinder and has said that if he gets anything wrong the players should point it out. I'm almost certain that just killing someone with magic doesn't destroy all their gear, but I can't find a good source to back me up.
I know that with a fireball, for instance, a natural 1 on a saving throw risks damaging one equipped item, and the fireball will damage unattended items. Conversely, the spell disintegrate specifically does not harm a subject's equipment. Is there a general rule about energy damage killing a creature also destroying its equipment?