Could Have The Aurora Massacre Been Prevented?

Could the massacre at the Aurora CO. theater have been prevented?  After thinking it over for the day, I can only think of a few things that may have stopped or slowed down the killing.
The one thing that bothers me is that the shooter was able to exit the theater through the fire escape and then come back in.  I would think that the theaters would want to alarm the emergency exits, if only to prevent people sneaking into the theater to watch a movie for free.  I suspect that movie theaters are going to start putting alarms on the doors.  If a theater employee would have noticed the guy walking out the door, they could have closed the door on the guy before he came back out.
As far as the guns are concerned, he purchased the guns legally and there were no signs of criminal behavior or mental illness.  He bought the guns from reputable stores and the ammunition online.  Even if you restricted gun sales, there are enough illegal guns floating around that anyone could easily buy a gun or guns illegally.  The Denver area has numerous gangs who engage in illegal behavior, gun selling is maybe one of those behaviors. 
People who think that controlling gun sales will reduce violence are just naive.  We have 200,000,000 guns in the U.S., so even if you suddenly stop manufacturing guns, we still have 200,000,000 guns.  Further, cities with strict gun control still have a lot of violence.  Chicago has some of the strictest gun laws yet, in two weeks, they will have over 12 murders, on average.  So, strict gun control is not the answer.
Further, the guy apparently knows how to make bombs as evidenced by his apartment it being full of bombs.  So, even if he had access to guns, he easily could have bombed the place, perhaps even doing more damage. 
The only thing that could have stopped him was finding out how he got his money.  If he was living off of student loans, then there was nothing that could have been done.  If the family was supplying him money, however, then maybe they had some responsibility in finding out where he was spending his money.
In the end, there was probably nothing that could be done to stop the killing yesterday.  The shooter is a very intelligent thug and determined and he would have found a way to kill one way or another.  Sadly, sometimes, bad things happen to good people.