This trophy is available during the following mission:
Please read the guide available for that mission to understand how to initiate it.
You will find this guy in the same apartment building you neutralized Double T during the "Cloak and Daggers" side mission (his apartment is literally across the hall
Take out the bodyguard that shot him full of holes, and then Brent will demand you get him some morphine before he says anything about anything. Brent's trauma kit is in his bedroom closet.
Inject him with morphine, and chat with him for a moment before he demands more. Give him another dose and he will get chatty again. Once you get all the info you can, choose "Leave" and Brent will request you give him another dose and put him out of his misery. Go ahead and this trophy will pop. PLEASE NOTE
: I am not certain if this trophy will negate "Pacifist" (since you are, technically, killing someone by your own hands
) but I would advise if you are going for that trophy, to make a save prior to speaking with Brent so you can simply reload the game after you obtain this trophy, and not screw up Pacifist.
If anyone can clarify whether this does nullify the Pacifist trophy, let me know either way in the comments below.