I would be surprised if Minnesota didn't have a bit of this. Anytime you get a bunch of people together with an event like this, you have a chance of this happening.
I had heard on the news that the Durham police and the UNH security were getting ready for this. They say this often. They just aren't equipped to handle these situations.
I remember back in my time there, a couple campus-wide snowball fights that ended in 100s of broken windows, injuries, and an eventual police response on the lawn of the president's office (Thompson Hall).
Luckily, it is quite easy to avoid these incidents. Even if she was there, she could have been quite safe in most of Durham. These problems mostly occur in the immediate downtown area (about 200 feet of road). The dorm area are normally not affected.
But yes, it is immature.
Ted