Thriller: Guy blackmailed by "friend" with photo after they kill bartender girlfriend who was cheating on them with each other.

[Heather]

The boy is overseas and begins seeing a bartender. He finds out she is seeing someone else as well so they make a pact to confront her. I believe they just wanted to scare her at first but end up killing her and taking a picture before burying her. They go their separate ways but the guy continues to blackmail him to doing what he asks with the photo. The main character does not want to take part in what the other guy asks him to do (I won't state because of spoilers :) ) but the other guy enjoyed killing the first girl and turns really dark. I believe I read this book within the last few years!

[Heather]

I guess it would be considered a thriller? Similar to popular authors like Peter Swanson. That’s who I thought wrote it at first but I’m not seeing it. I checked my kindle history and good reads history but can’t find it anywhere!