chosen because it was the only one that banned guns.

How do Multiple Victim Public  
Shooters Decide Where to Attack? 
John R. Lott, Jr.*


Why did James Holmes pick the Cinemark's 
Century 16 Theatre in Aurora, Colorado, to commit 
mass murder on July 20, 2012? You might think that 
he chose the closest theater to his apartment.  Or, 
that he chose the one with the largest audience.  Yet, 
neither explanation is right.  Instead the Cinemark 
theater seems to have been chosen because it was the 
only one that banned guns.  Out of all the movie 
theaters showing the new Batman movie that night, 
it was the one theater within convenient driving 
distance where guns were banned.  

http://www.acjs.org/pubs/uploads/ACJSToday_Sept_2012.pdf