I wouldn't worry too much about telling people who you are or where you're from. Likely you won't be hanging with the sort of crowd who is going to care, and those that might aren't likely to confront you in that sort of context, unless you are out looking for trouble, that is.

One thing I would strongly recommend to anyone out in public anywhere these days: If you see someone in public having some sort of an attack, or maybe fainting or otherwise having difficulty, go in the opposite direction, preferably quickly. Something I am seeing more of these days are suicide bombers with explosives strapped to themselves acting like they are ailing from something. As the crowd gathers around to offer aid/see what is happening, the bomber detonates his load and takes a whole bunch of people out. I saw it in Iraq, and I am aware of such events happening elsewhere with increasing frequency. It is a nasty ploy playing on both our good nature and our curiosity. There are variations on this theme, such as the alley victim apprently being attacked, etc only to blindside you as you attempt to confront the assailant they are in cahoots with. Much as you might want to help out people in apparent distress, or gawk at the event, it is best to evade the scene, try and contact the authorities, and let them deal with it while you go on about your business.