I agree that the narrator is jealous of his ex's new boyfriend, to the point of either imagining or actually committing murder. I always thought that Rachael was the ex, but now that I've read some of these comments I think Rachael might be a friend he's talking to, telling her to murder him because either he caused the breakup or because he killed his ex and/or his ex's new boyfriend.
I agree that the narrator is jealous of his ex's new boyfriend, to the point of either imagining or actually committing murder. I always thought that Rachael was the ex, but now that I've read some of these comments I think Rachael might be a friend he's talking to, telling her to murder him because either he caused the breakup or because he killed his ex and/or his ex's new boyfriend.