Hey there.
The story is simple - I played on the EU2 siege server (I think it happened a hour ago or something like that), I went to the back door and started to break it. Then some guy under the name of b0zkart teamkilled me without any visible reason.
Screenshot 1:
Screenshot 2:
As you can see, even my teammates were amazed by his action. I asked him why he did that, but he gave no answer. So I think the answer is - he is nab. And I think it is enough to ban him. Cheers.