Don't answer the door, tell them you are calling 911 to verify they their is a unit at your address serving a warrant. Instead of undertaking an active search for an intruder, take a defensive position inside your home, ypu have the tactical advantage of knowing your home's layout, why give that advantage up to find an individual who may lye in wait in the shadows for you to find him. Make him come to uou, use cover and again make contact with 911 and give them your name, address, and tell them that you are armed. Confirm that they infact are LE at your residence.
A modified version of this worked well for me. Years ago, I was up studying late and got a knock on the door. The front door to the apartment was about 3 inches thick and solid oak. I went to the door and opened it a crack to see who was there. (not the smartest thing to do, looking back, but I wasn't doing anything wrong, and had no reason to expect what happened next.) A plain clothes officer (according to him, I never saw a badge, marked car, lights or anything that identified them as LEO's) asked to see a Mr. Nessmith. I told him there was nobody there by that name. He hit the door with his shoulder before I could blink, trying to break in. I had my tennis shoe blocking the door from opening any further and the guy bounced off the door and back into his partner.
At the time I remember thinking Mean Joe Green couldn't have forced that door open with a 10 yard running start. I shut the door, dead bolted it, went to the phone and called the police. The two guys drove around to the back and started trying to break in my bedroom window. I had the lights out and was standing in the hall watching them. I told the police who I was, my address and asked the police if they had an officer named whatever. If they did, they might want to call him off. I told them that whoever he was, he was trying to break into my apartment window and if he succeeded in getting inside, they were going to lose him. It didn't take but a second for his radio to start blaring and somebody called him off. I figured I would be getting a visit later that night or the next day about the incident, but I never heard a word about it.
Having a solid front door, a secure place to retreat to and a phone in that location allowed me the option to deal with a situation, that was going wrong in a hurry, in a manner that kept everybody safe. Quick action on the part of the police department in calling off their officers was a big plus too. I didn't need any more coffee to stay awake while I finished studying that night.
