I am also aware of other measures, but it would be inappropriate to disclose them here.
Ah yes. I was in Rome a little while after the Pope got attacked (several years ago). I happened to be there on the day that the Pope was having one of his public audiences in St Peter's Square (or maybe he heard I was going to be there that day and had a special one? Who knows?) Anyway, I was equipped with a good telephoto lens, and there, up amongst the statues of saints and so on, was a bunch of cops/soldiers (hard to tell the difference in Rome) with a tripod-mounted machine gun. Fortunately, no-one within 20m of me made any terrorist-like movements.
Well, I don't think I'd be hitting the trigger on one of those unless I knew my principle was already well out of the way! They are hardly the most discriminating firearms ever.