I've seen some theories that it was actually an ADS (basically a low-power microwave beam, immensely painful but tuned to be just under the threshold to actually cause visible burns), since there haven't been any reported cases of permanent deafness yet. The student organizers in the crowd did an incredible job clearing people out of there before the police could escalate further and cause more mob-crowding panic dea…
Ah so these sonic weapons are indeed seriously harmful. I was wondering if hearing loss was a result.