This happened to me today as well, although from different people. The guy ninja looted 3 items for him and his friend and left. There should be some kind of global public blacklisting so that we may inform people about these guys.
I know, but you have to have a way to let people know that some are just scum! Today a guy ninja looted 3 items for him and his friend, in Siege of Orgrimmar normal. A guy who made a group through oQueue no less. I sent a ticket to Blizzard which I expect to be an apology of some sort but they won't do anything about it. Ninja looters still exist to this day because there are no consequences for their actions. You loot anything you want, Blizzard won't do anything about it and there is nothing anyone else can do about it.
I sent mails to their guild masters, I even spoke to 1 of them. He said the guy had beed reported to him as a ninja looter before and he was kicked from the guild, but the guild was of the social, money making kind so he won't care. There are only 2 ways he could be punished, lose the items and be warned or put in a black list and not be able to raid again and neither can happen at the moment.