Based on a book by Paul Lieberman, Gangster Squad tells the true story of the secretive police unit that took down real life mobster Mickey Cohen (Sean Penn). In the film, just as it happened in real life, this elite group of officers were assembled for their uniqueness and proved to be the one and only method of freeing up the choke-hold Cohen had on L.A. in the mid to late 40’s. Ruben Fleischer (Zombieland) wastes no time immersing us in what kind of movie this will be. Like a whirlwind we are swept up in a kidnapping in progress that shows us Sgt. John O’Mara (Josh Brolin) and his talent for following his hunches even if it most…