This happened to me countless times in the past 2 years, more often it was me killing others dropping their items. I killed Neil on Christmas of 2014 for him to drop 13 or so santa hats, fortunately for him I'm a stand up guy so I gave back and that's how our friendship began.

It DOES definitely happen with and without mage, but I've noticed probably 85% of the times it's happened was when the player was killed with a final mage shot. I'm 100% sure it happens wayyyy more often when killed with mage. I've been through this probably minimum 10 times over the years.