That is not true. You can carry concealed with a permit or open without a permit. I lived there for most of my life.
This ordinance banning the carrying of "dangerous weapons" was deemed "unenforceable" when Colorado state prohibited cities and counties from enforcing such laws in 2003. After talking to officials the Aurora Police Department, we found that counties can now issue concealed-and-carry permits, BUT in Aurora, it is still against the law to fire the weapon unless at a shooting range (or if you are an officer on duty). Therefore, it would have been illegal for anyone to fire in the theater. Also, the theater reportedly had a ban on any and all weapons. Anyone without a conceal-and-carry permit in Aurora must also keep their guns unloaded unless at a range.
** See Aurora Code Sech
ttp://library.municode.com/index.aspx?clientId=10331 It shall be unlawful for any person to fire, shoot, or discharge any firearm; crossbow; bow and arrow; slingshot; blowgun; BB gun or pellet gun, whether powered with gunpowder, compressed air, or gas cartridges; gas gun; or any weapon whatsoever within the city limits. However, such discharge, firing, or shooting by any law enforcement officer, federal, state, county, or city, in the course of his or her official duty shall not be deemed a violation of this subsection, and such discharge, firing, or shooting at commercial, private, or public shooting ranges or by authorized classes of schools or universities at all times under proper instruction and supervision as may be authorized or permitted by law shall not be deemed a violation of this subsection."
*** Aurora Police Department confirmed this is the case within the city limits and without a conceal-and-carry permit from the appropriate county. See Aurora Code Sec. 94-144.5.