On October 28, students joined forces with Occupy DC for a protest against crippling student loan debt. What was intended as an entry to Sallie Mae's offices for a discussion about crippling student debt bogged down into an arm-locked siege of the entire building after police arrived first. One of the cops brandished a giant pepper spray canister the size of a large fire extinguisher.
There is also a report that a protester with a trumpet had the horn destroyed by another cop. As protesters were approaching the target, the brass band was keeping the cops behind the protest. They didn't like that very much and the first confrontation was at that point. I don't know if the trumpet was broken there or later for revenge. Anyway, the brass band blockade leaked when the row of parked cars ran out and cops managed to pass the protest on the right at that point.

The cops turned up 7th st before protesters marching on Penn arrived at the intersection, implying they expected that the target had been reached. While Sallie May is in that building, their security staff has had long nasty experiences with protests attracted by Sanofi-Aventis and Bayer, two Big Pharmas with lobbying offices there who are customers of Huntingdon Life Sciences.

While most of the protesters pressed against the police line guarding the Penn Ave door, other teams deployed to all other exits and established an arm-locked semicircle of protesters at every one of them, plus a sit-in blocking the driveway.

It was at this point that the cop with the gallon size pepper sprayer appeared on 7th st. The display of a heavy weapon proved to be a provocation after what happened at Oakland, and came very close to causing the situation to escalate. Finally the cop with it went to the other side of the street for a short time to allow the situation to cool off.

The siege continued, a true siege under the slogan "We can't come in, you can't come out!" At one point, it took a determined push by multiple cops to get just one person through the siege lines.