This is done by shooting a LAM that has been placed on a wall and armed. You can do this with your own LAM at any point in the game, or you can wait until you see an enemy LAM on a wall somewhere. I suggest using something like the Sniper Rifle or anything with a scope to shoot the LAM as the blast radius is of decent size. You could very easily make a quick save beforehand so you don't lose ammo, your LAM, or your limbs.
