I guess the police had been told the man had a gun and was threatening to use it. Then when they got to the house there was no action, no activity, so they knocked on your door to see if they had the right house. When a person is in a home with a gun, the police will respond and treat it like a standoff and block traffic for blocks while they negotiate. Since the man inside didn't do anything they wondered if they had the wrong house. They were ready but nothing was happening, so they left. Then came back when something finally did happen. That's how I interpret it.