I have read posts here, and also some news articles, that suggests that one or more of the different terror groups doesnt trust their martyer canidates very well. Their bombs are fitted with a hidden radio reciever as well as a timer and the expected manual detonator.
The bomber is followed- without his/her knowledge, and if there is any sign of chickening out they blow him/her up.
The timer is in case security gets too suspicious and decides to shoot your bomber. Then they have to call the bomb squad and evacuate the area, and the handlers can slip out with the crowd during the evacuation.
In this case, since the bomb went off and he is still ALIVE, it appears we might have a chicken. He tried to take off his bomb, and because it wasnt fully around him when his handler set it off, he lived. He must of also broken up the charge in trying to jettison it, cause he looks to be in entierely too GOOD a conditon to have been exposed to the usual bombers payload.
Perhaps he ripped out the detonator, and then only it exploded and not the charge?
Another thing, during the raids in the Occupied Territories, there were a couple attempts made by suicide bombers that were foiled by their premature explosion. Speculation is that the IDF has confirmed the use of remote detonation of suicide bombers and is using RF signal generators to induce premature explosions...
Like I said though, this is all speculation...