The Mystery of Violence!

Just back after watching "A History of Violence". I am no great fan of Viggo Mortensen (will leave that to the ladies!) but the movie just didnt make sense. At the end, this is my synopsis: The guy gets tangled up with some rough types. Shoots them dead. Gets a call from the hoods boss. Shoots him dead. Gets a call from the boss's boss. Shoots him dead. End of movie. I havent read the comic (btw they call them Graphic Novels nowadays :P ) it is based on, so i wasnt familiar with the plot to begin with...then it got worse!