Ending like History of Violence

I just the final scene where Mickey is standing over the husband and about to pull the trigger, that Diane Lane would be standing there with the pistol. Instead of the son shooting the assassin and saving his fathers life(like in History of Violence) it was the wife who did what Mickey thought she couldn't do. In real life, that female cop shot and killed that officer who killed all those soldiers at Fort Hood last week. Don't underestimate a woman!