The problem with asking us to assume we have already engaged the shooter is that many of us are in the mindset that we would seek other options first, such as extraction of ourselves and company. So, having us in a scenario in which we have already acted against our own thought plan makes it difficult to answer accurately.
Of course, the original inquiry could have been worded differently, into a scenario in which the respondent was cornered already, in such close proximity to the enemy, that immediate engagement was an appropriate response. Many of the responses given, including mine, would still fit.