Maybe somebody else was to pick up the car to use the bomb material and failed to get the car before the police did.
Then that somebody else would be more senior person (hard to think of a 19yrs old as the boss) in the terror organization - and would probably be doing bomb distribution himself. It doesn't look like they have too many bombs to spare, for the bombings so far have been blessedly rare. If it was the car of the 19 yrs old, I would very much doubt that he got blown up, and would rather suspect that he went underground, hoping to retrieve and use the remaining bombs.