I just heard the two other people have been released. It seems to me that any such event is followed by hours of confusion. I am guessing (hoping?) single gunman.
If 1 or 2 others are involved then its no longer a nutcase on the rampage, its a planned act of terror and in that case my guess would naturally be that they suddenly decided to give their lives for Islam or some such craziness. As a muslim, I hope that is not the case...