Questions, questions

How long does something like that take? When do they do it so that no one interrupts them? How far do they travel to leave their mark? Who does something like that, and why? I assume vandalism is all about making a mark on the world when there don't appear to be any other options. Or at least not any easy ones. Is there a way to stop it by getting the perpetrators to feel more connected to their communities, or will there always be disconnected individuals damaging our public spaces?