BSI Scene safe? No? I'd render aid to the victims of the attacker... but sorry to that attacker, I'm going to treat them last if at all, EMT's have to think of themselves first and foremost, then their team (or in this case, the other victims). Never put yourself in a position that you can be attacked or taken as a hostage, if you have someone crazed enough to attack you in the first place... who says they are not on say they wouldn't take you hostage right when you go and try and help them in order to beg for their freedom?
But on that note, I have a first aid kit in each of my cars in-case something happens, I rarely carry any of that with me on my person though, at the most some medical tape but thats it... really you can use that tape and do anything with it, shirt for a bandage or tourniquet (or tape for a tourniquet), SCW tape a CC, an ID, whatever with a flutter valve and presto you're done.