You're both misreading the question. The question was not "how often do police go in expecting a shooter?" The question was, "what 'probability of there being a

You're both misreading the question. The question was not "how often do police go in expecting a shooter?" The question was, "what 'probability of there being a shooter' justifies going in armed/with a protocol that expects one?" User:shadowgovt, if you followed the thread, was asking us to be outraged that they went in when it was "only" 7%: https://news.ycombinator.com/item?id=32259925 https://news.ycombinator.com/item?id=32259925 But yes, "tighten up" those Fermi estimates for a question no one asked and which has no bearing on the discussion.