Instead of giving the police and investigators time to solve the murder case, he takes actions in his own hands
Jack is a father who is frustrated. He is understandably going out of his mind over this affair. He thinks he knows the truth of his daughter's murder but he just doesn't have the proof. So ,yes he is frustrated with the "due process" of the police. He takes matters into his own hands out of all the emotions that are tearing him apart inside him. Jack is taunted by his daughter's killer, he is cheated on and has a fight with a baseball bat. Really how much can a guy take before he becomes a vigilante?
Mr. Salmon is losing his mind because they have yet to find justice and he thinks he knows who murdered his daughter. Yet he has not one proof of evidence Mr. Harvey killed his daughter. So he is slowly yet surely losing his mind due to the lack of police work.
