This is unlocked during chapter 2 after an unmissable fight.
*** Spoiler - click to reveal ***As you progress through chapter 2, you will go back to Rusty's cabin at night. First you will find him severely wounded and is asked to turn on the lights. Finish this objective (or try to) and when you are back Rusty is no longer there and has turned into a Taken. Battle him as usual by shining the light then shooting him until he disappears and the trophy will unlock.