The car bomb at the beginning of the movie, and near the end of the movie are supposed to be the same event.
At the start of the movie, the bomb blows up with Ace (de niro) still in the car.
At the end of the movie, the car ignites on fire first, then Ace gets to escape, then the car explodes.
few more interesting things,
1. if you watch the car bomb scene at the beginning closely, you can see that de niro suddenly turns into a mannequine before the car explodes!
2. at the end, even though the explosion seems to occur during bright daylight, when the ambulances are at the scene to take him away it is pitch dark night time.. gee.. slow ambulances!