Stairs are a tactical nightmare. Most people don't even begin to understand how complex they are as a tactical problem. They are even worse than hallways. For starters, you are fighting uphill, usually in an enclosed space. There are different types of stairways that all require different tactics too- internal, external, spiral, opposing, handrail spacings that offer loopholes to a shooter from above, with or without intermediate landings that come with or without intermediate access, and so on. Also consider the fact that various objects can be thrown down them with the aid of gravity. Just stand at the top of one of these, get low, and gaze down into this dead space and have someone come up the stairs, and see how often portions of there body are exposed as they ascend- no matter how thy do it. . If someone takes a hit to the lower extremity, he is going down, and presenting an obstacle to whoever else is going up behind him. We trained on stairs so much that I dreamed about it. With the aid of simmunitions, the biggest lessons learned are that there is no good way to do it (even as a highly trained team) but there are several ways to do so and prevent a slaughter. The other lesson is to avoid going up stairs if possible. During Neptune Spear (the UBL raid), the SEALS had planned to rope from their helo to the roof to gain access to the "high ground" to avoid this doomsday scenario (of course, that didn't work out, and they had to go up, fortunately they were able to pull it off). Also, US urban combat doctrine teaches that the best way for a defender to cut off stair access is to deploy a roll of concertina wire (the combat slinky) in a stairway. That will stop any stair assault dead in its tracks.It is so effective, there isn't a need to even post security at the top of the stairs. If concertina wire isn't available, broken glass scattered on the stairs will allow a shooter to know someone is coming up well in advance. Short answer? Call The police. Clearing stairs (especially uphill) is the job of a highly trained TEAM.