@Avi – sure, the UK has trouble also, but generally I believe France is worse.
By the way, the same things happen in E”Y. Remember the Merkaz HaRav massacre? I lived almost around the corner there when that happened.
The worst part of this is that you can never entirely prevent it. One who wants to commit terror attacks can easily do so – even if it’s just a single person with just a gun and a scooter. He could do it another 10 times and get away with it each time. You simply cannot put armed guards everywhere, on each possible location; a person cannot be alert to that level continuously anyway, so the guards themselves might get killed easily as well.
Ultimately I doubt the perps (I doubt it’s just 1 guy) will get caught, due to serious research, old fashioned detective work. But they’re not going to get caught by an armed policeman standing in front of some school.