I agree with you Hamas , Fatah too, have problems in their own territorys..and if it was a isolated attack by a small group, example , the slaughter of the Israeli family by kniife wielding young Arabs, hard to know all such events, on what I think was a spur of the moment thing..or put up by a small isolated cell with little past experiences, but this attack was so well coordinated, so many moving parts of..not just a quick attack and out they go...hard to beleive something wasn't known.
I also wonder , if known how much effort would be put intion it to stop it, or if the group, al Quidab possible, the threat against them selves from them if they interfeared with, might have been to much for them..esopecially just o stop some jews getting killed, the desire just not there, evn with the possiblen Israeli response..
However, Begin did it back in 1948, Jews stopping, killing other jews , the Irgun, Stern gang..only three years after the end of the war and the end of the slaughter..for jews to go after their own fellows, evn if the politics were different, just not a happy occurence, but Begin knew it had to be that way, one force, one voice and no private armies..the problen of Hamas, Fatah, they are not yet willing to make that same commitment..