Now- for the rest of the story...
This is how the situation began from the viewpoint of the police:
At around 4am on a weekday an officer was dispatched to a residential alarm. No big deal...97% of B&E alarms are false alarms.
He gets to the house, walks around the perimeter and finds a single family home with two cars in the driveway. There is poor lighting around the house and 1/2 of the perimeter is concealed by a fence and bushes. The patio door, that is concealed from view from the road, is open. He looks into the patio and sees what looks like fresh sand on the rug inside the door and a pair of shoes a couple of feet from the door. The alarm activation was reported, by the alarm company, as coming from the patio door. It is now about 10 minutes from the time the alarm was activated.
The officer has worked the area for 3+ years. He responded to and was first on scene, less than a year before, to a real home invasion at a house across the street. That call involved multiple suspects with handguns and rifles. He has responded to dozens of calls of drug activity in the immediate area during that time. He is aware of dozens of gang related assaults and robberies within a few blocks. He has responded to multiple murders in a nearby housing community related to gang activity. He knows the neighborhood to be a good neighborhood with respectable residents but plagued with issues brought on by the proximity of the nearby public housing community.
The officer requests backup. About 10 units respond including a Sgt. (It's 4 am on a weekday...they were bored) They all park about a block away and walk up to the house. Officers surround the house and five officers go to the open door. The hoods of the two cars in the driveway are both cold. They request that dispatch call the house and try to make contact with the residents. The only number they can find is the one that the alarm company gives them. They try it once and receive no answer. The Sgt. on the scene says something to the effect of "Call them again. No one wants to go in and surprise an armed resident if it can be avoided. They can hear nothing from outside the house and dispatch reports that there is still no answer.
The 5 officers behind the house have already acknowledged the possibility that there could be a legally armed resident in the house. So after two tries by phone and no answer, and based on the totality of the circumstances outlined above, the decision was made to make entry.
The point officer (Ofcr A) pushes the door all the way open and announces " POLICE OFFICERS, POLICE OFFICERS, POLICE OFFICERS, ANYONE INSIDE COME OUT WITH YOUR HANDS UP!" as loud as he possibly could… No in reply…they enter. It was an enclosed addition to the residence with several rooms that were cleared without finding anyone. Ofcr A was holding at the main door to the residence…hoping was locked.
It wasn't.
Ofcr A pushed open the door and again announced, several times, very loudly. They entered into a living room area and the Cpl. who was 3rd in line gave two more warnings. (The Sgt. later said that he could hear them plainly outside and was waiting for the neighbors' to start turning on their lights to see what was going on.) There is still no reply from inside the house.
Ofcr A begin to enter a hallway with 5 or 6 doors when a door opens at the end. He shines his 800 lumen light at the door and a man wearing shorts comes into view. The officers are yelling " POLICE, POLICE, HANDS, LET ME SEE YOUR HANDS, HANDS!". The guys stops and holds his hands up. Ofcr A ask him if he lives in the house and he replies that he does. They turn on the living room light. He can see that they are uniformed police officers. He says his wife was in the room with him, and a large rotty mix comes out of the room barking. The homeowner says that the dog hadn't barked until he had heard the officers yelling and he had opened the door.
They tell him that there had been an alarm activation in their residence, they had found a door open and the door to their house unlocked. A search of the rest of the house showed that no strangers were inside.
They spoke with the residents and found out that one of them had walked the dog earlier, the door must not have closed all the way and the wind blew it open. Of course, both thought they had locked both doors. They only had cell phones, the wife was the one that had her number listed with the alarm company. Her phone was on the kitchen table… on vibrate...with 2 missed calls from the police...the husband's number was not on file anywhere.
And the (big damn) dog wound up being worthless...if it had been sleeping in the living room or kitchen it would have woken before the residents and would have at least woken the residents.
So now you know that there are the legitimate reasons for the police coming in your residence, seemingly unannounced, for no apparent reason…a search warrant isn't the only reason the police may enter your house. You don't have to be a drug dealer or a gangbanger...you just have to have an alarm and not lock you doors
The responses here have been pretty well thought out. Showing that you aren't a threat would be the big thing to remember...please don't yell and charge them.
If you are caught in the hallway, whether armed or not, shooting it out isn't the survivable answer...this isn't a video game where you get points for the number of BGs you take down with you.
Closing the door isn't a bad idea, if you are thinking that clearly at that moment, as the logic of LEOs not usually shooting through doors is well thought out. A stand off may buy you time to call 9-1-1 and clear up what is happening before anyone gets hurt.
Personally, I would not have armed myself and answered the door either. If I knew no one should have been in the house and I heard voices shouting, I would have grabbed my gun and cell phone, grabbed the wife and hustled her into the bathroom where we would be in a defensible position while calling 9-1-1. Having children does make it more complicated and you'll have to plan accordingly
I hope this has provided some food for thought and given you a different point of view of things that happen in real life