LOS ANGELES—Although  Gangster Squad is based on real events, Zombieland director Ruben Fleischer’s ardent homage to film noir runs very little risk of being taken as truth. It’s a good-looking romp around L.A. in its halcyon heyday, punctuated with plenty of girls, glamour, and gangland-style shoot-’em-ups.

Josh Brolin and Ryan Gosling play renegade cops who are called upon to rid postwar Los Angeles of its scourge, Mafia boss Mickey Cohen, by any means necessary (it doesn’t hurt that Cohen is played by a scenery-chewing Sean Penn). It’s a genre caper where Tommy guns and sidearms costar along with A-listers eager to do their best Bogie; where both the good guys and the bad guys are shown executing their foes at close range, and it’s all in fun.

However, recent events have cast a pall on the movie industry’s fun-gun approach. Gangster Squad wrapped just before the massacre in Aurora, Colorado (The Dark Knight Rises, another Warner picture, was playing at the time of the shooting). Subsequently, the studio reshot the film’s pivotal shootout scene. Previously, the scene took place in a movie theatre, but it is now a tense, atmospheric, and much less graphically violent confrontation on the streets of Chinatown.

At the L.A. media day for Gangster Squad, which occurred one day after the Newtown, Connecticut, shootings, Brolin and the rest of the filmmakers addressed questions about specific changes to the film as well as on-screen gun violence in general.

“We’ve had a lot of things come up lately that make it very serious,” said Brolin, whose character in the film, Sgt. John O’Mara, is a square-jawed cop and former war veteran who is fond of using bullets to solve problems. “It was a lot of fun doing it, but at the same time, for a guy who doesn’t have any guns myself…I get a little nervous.”

Brolin, who calls himself a “seventh-generation Californian”, was on the other side of the law in No Country for Old Men, a film about violence as a defining characteristic of the American landscape. He has also wrapped Spike Lee’s remake of Park Chan-Wook’s Oldboy, a film that’s unlikely to be rated G. The original, notorious Korean thriller depicted violence (specifically, revenge) as an immutable component of the human soul.

“Of course, there’s a sensitivity,” Brolin continued. ”But you have to look at the grand scheme of things, from a universal standpoint…There are many, many different factors…There’s always been violence in movies and there always will be violence in movies. And whether it lends to the one psychotic who’s out there and thinking the worst thoughts you can possibly think will always be a mystery.”

For his part, Brolin said he preferred another fight sequence, where he and Penn eschewed guns for fists that “were flying wildly, in the hopes that something would connect”.

“It was a tough fight that we rehearsed for many, many, many, many weeks, and I love the way it turned out,” he said with a grin. “I think both of us being the current and ex-smokers that we are, it was the most challenging.

“We work similarly, and we have a lot of fun on the set,” he continued. “And then, when you’re looking at somebody in the pupil and they’re doing their best to be as intense as they can and you’re doing the same, and you know each other as well as we do, it’s also kinda dumb.”