This is Book Zero of the Mackenzie August series.
Imagine your favorite teachers from high school are dying, being mysteriously murdered one by one soon after the arrival of the new English instructor...
Mackenzie August is starting a new life. After a successful but destructive career as a high-profile California homicide detective, and then a less successful and even more destructive stint working for a church, he has moved to Virginia to start over as an instructor. The only thing he's bringing with him is Kix, his infant baby boy. He plans for peaceful living with his son, but trouble soon finds him as his new co-workers begin showing up dead outside of his classroom.