Lone Star Payback by Delores Fossen

Former military special ops officer, Marco Morrelli, finds himself at the center of a deadly game. As an elite security operative for Maverick Ops, he thought he had left the battlefield behind. Little did he know that a faceless adversary, calling themselves “Your Biggest Fan,” is systematically eliminating Marco’s enemies and those who’ve crossed him.
Caught in the crosshairs is Rayna Brandon, a skilled operative in her own right who shares a turbulent history with Marco. Their paths collide once again when Rayna’s name unexpectedly lands on the hit list, marking her as the next target. Forced to confront their past and set aside their differences, Marco and Rayna must join forces to unravel the mystery behind Your Biggest Fan and stop the deadly rampage.