That's, like, a double bad thing to do; maybe even triple. Someone should have told these scumbags that there are clearly marked signs saying that guns are illegal on campus, and then showed them D.C. Official Code 7–2501.01, and then, perhaps, told them that robbery was illegal as well. Then maybe they would have gone home peacefully.
Common sense folks.
And as you can clearly see, it is totally reasonable to make adults defenseless because you never know when an armed DHS officer will stumble upon your accosters and save the day. There's nothing to fear!
Update: It's another one!