Gangster Squad is an upcoming crime film directed by Ruben Fleischer, from a screenplay written by Will Beall, starring Josh Brolin, Ryan Gosling, Nick Nolte, Emma Stone, and Sean Penn.
It is the story of LAPD Detectives who are attempting to keep Los Angeles free of gangsters during the 1940s and '50s. The film was originally set to be released September 7, 2012, but in the wake of the 2012 Aurora shooting, the film was bumped to a January 11, 2013 release date by Warner Bros. Pictures.
We aren't handed ammo within the barracks limits (usually, there are a few exceptions), let alone indoors and when the training is over everyone's gun/mags is confirmed to be empty, and if there's bullets left they're either shot away or given back.
Also it wasn't a real bullet, but a blank which is usually shot when a blank-firing adaptor is attached (making it harmless, unless the adaptor is loosely fitted and flies out when the gun is fired), but without it the bullet is lethal up to 50 meters.