The Quarry is a heavy story-driven horror game that every decision you make will change the whole outcome of the game. Even going after trophies can result in some characters’ deaths. Let’s see how to get the Mutually Assured Trophy.
You will be able to do this while in Chapter 9. When nearing the end of the chapter you’ll get to a sequence where Ryan and Laura will crash and fall down through the floor with Chris in Monster form.
Once down, you’ll get up while playing as Ryan and holding a shotgun in your hands. The crucial thing to do now is not to shoot Chris. It will result in his death too.
At the end of the chapter, you will get this trophy unlocked. Congratulations!