When Mr. Grainger is lying in the street, a man in a car comes upon him. The first shot is from inside the car. There appear to be small leaves on the hood and the lower part of the windshield. It may be drops of water since the scene takes place just after a rain shower. However, when the driver exits the car in the next shot, the hood and windshield are both clean and dry.
When the boy sets the neighbor's house afire, it clearly starts in the upstairs window. But when the house is shown on fire shortly afterwards, it's clearly archival footage of a single-story house fire.