This one in Michigan, the scumbags forced their way into the home. They had badges and radios, and the home owner approached them thinking they were cops. At least he had the common sense to evacuate his family beforehand.
I've talked about these before.
Nothing good will come out of letting a random cop into your house if they ask you, so make sure you challenge each and every one of them by asking for a warrant signed by a judge. If you are the one who called the cops for something, than that's different; I'm talking about when someone alleging to be a cop knocks on your door. Of course, what actions to take if they don't show you a signed warrant and bust down your door is up to you personally. Be careful.