His brother.
It was a surreal scene to watch play out. Older brother waving a cartridge in front of the muzzle of a gun and the younger shouting "I'll shoot! I'm going to shoot!" I was completely stunned when to rifle went off. I'd seen them do stupid stuff before, particularly the younger one, but this one took the cake.
BOTH of them were raised around guns and in hunting families. They BOTH knew what a rifle was capable of. I never dreamed that he would pull the trigger.
I basically cut all ties with the two of them. We were best friends and hunting buddies, but with that crap going on, I valued my skin more than a hunting partner. I can find a new hunting buddy, someday...
Over the past few years, I've debated who was to blame, and have some to the decision that they were both equally at fault. One for putting his hand in harms way and the other for squeezing the trigger when he knew that there was something in front of the gun that he did not want to shoot.
I can't get around it. I have at various times blamed one more than the other, but in the final wash, they were both idiots.