I've tried the solutions others mentioned, but simply couldn't do it their way. I figured a much easier way to do it, without any special weapon or anything.
(This is a little while after the beginning of Chapter 1)
When you enter the area, kill the 2 Necromorphs at the start, and go towards the grind moles, a Exploding Necromorph should spawn (With the big orange hand) in the vent in front of you, kill it as fast as possible.
Then numerous Pack (Small children with long nails) should spawn, just run back to the beginning of the Grind mole, and use your Stasis to slow them down, then walk to the side, and simply PUSH them inside the Grind Mole. (Just walk against them) Just make sure you use Stasis numerous times to keep them sustained.
Then you should unlock the Achievement.
If you have questions, ask and I will respond.