MIT evidently added a camera. Later that day, the MIT police made their first contact with him.

https://en.wikipedia.org/wiki/Aaron_Swartz#United_States_v._...

"When it was discovered, a video camera was placed in the room to record Swartz; his computer was left untouched. The recording was stopped once Swartz was identified,"

IME, months-long internal investigations in an org with Secret Service involvement would be unlikely to escape senior management, but I'm just speculating and only have the same info as everyone else. You might be right.