Photoshoot of course, but, that isn't a flash mob.
Flash mob, a small group of people make an organized event for an area, wander around in it, along with people who aren't apart of it, someone gives a signal and everyone starting doing the same thing, like a random pillow fight, or dancing. Me and my friends want to do it, but it isn't fun unless you have a decently big group of people.
And wow, happy I didn't go to that.