Targeting Celeste by J.W. Ashley

Zach Murphy has a target painted on his back.
When Zach’s ex-wife resurfaces after years of silence, he’s determined to push her out the door just as she did to him all those years ago, but she refuses to go without issuing a warning. Zach’s in danger.

When those around him start dying, Zach sets out on a hunt for answers and discovers a trail of clues leading back to Clayton Matthews and a dead crime boss in New York. As he searches for a connection, he’s forced to turn to the one woman he never wanted to need again.
The last thing Celeste wanted to do was return to the city filled with painful memories of a future she’d only ever dared dream about.
When her ex-husband’s name ends up at the top of a hit list, she is pulled back in to help figure out who’s targeting him before it’s too late.
As old flames spark new life, Zach and his ex-wife are pursued by a deadly hunter who won’t stop until they’ve both been terminated.