One of the more insightful discussions of police sidearm choices that I have ever seen, back in the day when police forces were in the middle of converting from six-shooters to large capacity semi's, talked about the round count of officer-involved shootings.
With revolver-armed police, the round count typically is 2 or 3 rounds, or else 7. With semi auto armed officers, it was frequently the same two or three rounds to a stopping hit, or else the whole 13, 15, 17 19 or whatever was in the mag and the one in the pipe, plus one.
The explanation is simple. Either the gun comes out and a sight picture is taken and the trigger pressed, and hits happen, or the gun comes out, thrust towards the suspect, the trigger jerked until the noises stop, and during the reload, the officer, if still standing, remembers things like the sights on the end of his piece, and to press, not jerk the trigger. Me, I always would have rather only spent a couple of seconds wasting six rounds, than having to suffer through incoming fire while I emptied a 19 round mag. Lousy logic for weapon selection I know, but, it is hard to deny human frailty.
Watch modern trained officers wildly empty their self-loader when taken by surprise. As a private citizen caught in the wrong place, I have always been in favor of a fecal storm of six un-aimed rounds loosed in my communty, than twenty.