Security at a busy shopping center for the last 5 years. When it does happen, it's almost always teenagers.
We don't do anything about it. Not sure what we would do. Obviously, if there is context like someone is laying on the floor, visible injuries, or it's after-hours, we would check it out. Just some random person walking by and waving at the camera? Not suspicious by itself and does not even register on my list of priorities.
Lol, I feel like that falls under the context category.