You can get this achievement at the end of the first mission (F.N.G.). You will need to shoot 10 targets and throw 2 flashbangs. If you reach a certain accuracy, one or a few seconds are taken away from your total time. So it is key to
- Keep running and shooting
- Shoot the targets with as few bullets as possible.
Here's a video of me getting the achievement (On x1)
You will also need to run this mockup in 15.1 seconds or fewer for this achievement: