In Dubus's Killings, what moral conflicts does Matt battle?

Moral conflicts have to do with a person's inner struggles (inner conflicts) with what they believe to be the difference between right and wrong. People also have inner conflicts when they argue with themselves about an issue and what to do to solve it. Matt Fowler knows that killing is wrong, but after his son Frank is gunned down, the repercussions are more than he can bear. For example, his wife sees the murderer, Richard Strout, around town because he's out on bail. Matt is upset that his wife doesn't feel comfortable to venture out into her own town because she's afraid she'll see her son's killer. Matt says to Willis, "She can't even go out for cigarettes and aspirin. It's killing her."

Willis asks his friend how often he thinks about the murder and the weight of it on his wife's shoulders. Matt responds that it is interrupting both his and his wife's life. So, the dilemma is how to go back to living a normal life with the killer living in such close proximity to one's family--kill the guy?

Another moral conflict that Matt faces is the fact that his son Frank was dating Mary Ann, Strout's wife, while the couple was estranged but not divorced. His wife tells him, "She's not divorced, yet," but he tells her that he sees Frank's dating Mary Ann as a "positive thing." Since she married a jerk, and Frank is making her happy, the situation is good all around. Matt's wife Ruth asks him to talk to Frank about it, and he does, but he doesn't convince his son to stop seeing the married woman. Had he been successful with that, maybe Frank would still be alive. During these flashbacks, Matt struggles with whether or not it was fine for Frank to be seeing a married woman. 

What's interesting with this story, though, is how Matt does not struggle with the final decision to kill Strout. Sure, Matt thinks about the wife, children and mistress who will mourn Strout's life, but that isn't enough to deter him once he makes his mind up. Matt takes no pity on him when Strout tries to explain why he killed Frank; he doesn't even flinch when he lies to Strout about relocating him to another town out west; and he doesn't think twice when Strout tries to run and he systematically unloads a few bullets.