How could you see that the father was put under pressure?

Christopher's father looks after Christopher, knows all his habits, and understands the way Christopher works, but when he finds out that his son is trying to solve who killed Mrs. Shears' dog he becomes unusually angry and impatient. We learn that he killed the dog and that he lied about Christopher's mother being dead, and this prompts Christopher to leave home and make his first journey alone.Chris's father struggles to raise Chris on his own.