The home of Charly's mother shown in the film, with its distinctive yellow color and columns on the porch, is the youth hostel outside of Cassis near Marseilles at La Fontasse. Its location in Google Earth is at 43°12'59.78"N and 5°30'35.53"E.
'Richard Berry' (av) originally wanted to hire James Newton Howard to compose the film's music, but eventually set his sights on Klaus Badelt after he was advised to listen to the music he composed for Anything for Her (2008). After meeting with Badelt and showing him the film when he learned the composer was in Paris, Berry was pleasantly surprised to hear him say that it was him who was asking to score the movie, not the other way around.
Towards the end of the film, a man is eating a slice of pizza and telling a young man playing a video game what to do. He turns around and the slice he is eating is suddenly less eaten than it was before.
When Charly Matteï is driving and looking for an empty parking slot, his car has a major crack in his windshield. After finding a spot and shutting down the engine the crack is gone.
While Mattei is in the hospital the retrospect shows a young boy wrapping the gun handle with electrical tape. The idea is to make it impossible for the police to pick up fingerprints after the killing. However, he's using the wrong kind of tape - the smooth one instead of the sticky rough one - which renders the whole process useless.