In the library, I found someone holding a camera to take pictures of their children reading. What happened?

It may be that a professional photographer is creating, or that a photographer is collecting ideas, or that a boring person is doing something boring, or that it is intentional.

Whatever the reason, just go and ask. If it is a sneak shot, it can be stopped immediately. This is an invasion of personal privacy. If people are not malicious.

Then use it to pose, and you can have a wonderful portrait photo.