it is released now that 500 tons of weapons was seized by Israeli commandos during a raid on that ship...
and i think commandos had got a hint prior to their action, where and what to look for...it is obviously that it must have been something that provoked the Israelis and triggered their actions... I can not imagine that armed soldiers began firing on "peaceful" volunteers for no apparent reason... may be they are violent, but they are definitely not stupid idiots...
http://online.wsj.com/article/SB125732536158927651.html