Unfortunately, I wasn't able to get video evidence of this occurring, but there was a clan in Iron Banner, where every time you killed one of them, they would drop heavy ammo. Not sure if this has been reported or Bungie is aware, but if they know how to pull off this exploit, I'm sure others do or will. I have reported the members of that clan.
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Very rarely when someone kills me i drop a heavy brick when i never picked any up.... But for a whole team to do it seems kinda odd!