Somebody who attended a noontime business function at the Back Bay Hilton today reports:

An angry mob of between 200 and 300 union construction workers who had been demonstrating peacefully outside the hotel entered the lobby, throwing trash on the floor and chanting, "Hilton unfair to workers." The hotel could not function during this time as the demonstrators filled every inch of the lobby with guests and hotel employees looking frightened. The protest blocked Dalton Street and even the 39 bus line. The demonstrators finally left the building after Boston police responded with the special operations unit and threatened to start mass arrests.

At issue: A multi-million renovation project involving non-union contractors.