Kill 2 Helghast with 1 shot from the BP-02 Pup launcher

Chapter: Vekta Evacuates
Level # 1

After Private Billinghurst guides you through some burning office rooms and into an open space, go straight ahead instead of taking the stairs on your left. The Pup Launcher can be found inside the only room on the floor. After grabbing it, head upstairs and you will encounter three Helghast troops. Aim and fire the launcher at one of the enemies, and it should kill all three of them earning you the trophy.