Drug Addict

Probably not the inner-city stereotype, which doesn't fit easily into this game. Instead, have the classic middle-American addict: someone who had a back injury, got addicted to Oxycontin, and is now completely hooked.

This plot only works if there is a pusher in game. One possibility is that another character has been faking that an old injury is still around, and has been selling off their Oxy. For this to be interesting, there needs to be a connection that is difficult to make. Perhaps one of the victims was the supplier, and the buyer now needs to ransack their office looking for pills? Perhaps the police might find the pills first?