Friendly Fire: a Seth and Ava Mystery (Seth and Ava Mysteries #3)
Claudia Hall Christian

Standing in the lobby of the place that had restored him after two tours through the blood and muck of tunnels of Vietnam, Seth is drawn into a mystery that will take him through the meltdown of Reactor Four at Chernobyl to meet Russian Olympic marksmen and discover that a familiar demon is covering its tracks.
In the end, Seth learns the most important kind of Friendly Fire from a man who’s suffered horrific trauma and a woman who’s lived through the very worst life has to offer.
If you like Seth O’Malley, Friendly Fire is the book for you.