Heres a quick guide on how to get this achievement
Blood, Sweat and Tears
Start the mission and try to get a shotgun as early on as you can, keep this shotgun all the way through. Play up until the point where you have to destroy the van, once you have destroyed the van the Police will come into the building. They basically set themselves up for the achievement. Equip your shotgun and kick the door down, from now until near the end of the level there will be 6 police officers, storm them and shoot each one once, when you reach the doorway at the end you should have the achievement.