This is for completing the story mission of the same name. It's the first gun-focused mission about a quarter of the way through the game.
It starts with melee, clear them out and move on. Eventually you'll run into your target, Siu Wah, and at that point people start shooting. Do a vault disarm on the first guy behind cover and take out the rest. Note that explosives are highlighted in red, which can help clear them out a little quicker.
Chase down Siu Wah, then use him as a human shield to get out of the place. When the cops show up and Siu Wah escapes, you'll be on a motorcycle chasing after him. Do an Action Hijack here to recapture him.
Bring him to the mission marker to pop the achievement.