True but it wasn't a violent crime. Still wrong and stupid. I had a friend who streaked across the pep rally stage in high school. Everyone knew who it was but couldn't quite make out the face. That was silly and a fad at the time.
I have no idea what kind of mental illness motivates someone to expose themselves like that. It's bizarre.
I assume such people are, as you say, mentally ill and are testing the perimeter of the defenses, as it were. Seeing what they can get away with. Then they escalate a bit, see if that works. This guy tested a strong point in the defensive line, unfortunately for him.