No, you ARE following Rule 4.
As long as you can account for all innocents (i.e.: either with you or none at all), the target is clearly identified as having the ability and opportunity to kill you and is placing your life in danger. You know that whoever is on the other side of that door should not be there with the obviously exhibited intentions.
In my case, if someone has fired a shot in my house and is kicking in my bedroom door at oh-dark-hundred, he IS a target. I know where he is: right on the other side of my door. No innocents to worry about; I live alone and nobody has any reason to be in my house without polite entry. The backstop is also known: the rest of my house will stop any rounds fired. In the scenario given, I know my target.
Recognize that the application of Rule 4 depends on circumstance! Do not violate it, but know its application. If innocents are in the house and not with you in the given scenario, DO NOT FIRE because in that case you cannot properly follow Rule 4.