Seriously they've got cameras everywhere else in the building, why not in the concourses? When you have a younger crowd with alcohol and everything else, there's bound to be potential for stuff so they need to plan accordingly.
The Celtics have, over the years, been very weak in the area of policing stuff in the upper levels. They're getting a little better but crap like this - while not preventable - can at least be dealt with more effectively in terms of follow up.
They of course had a stabbing inside the arena a short time ago - and they're supposed to frisk people coming in. I'd say Wyc needs to consider finding a head of security with a bit more competence.