Shielding Abigail-Delta by Jennifer Becker

Aaron "Hound" Bradford has only ever had two loves: Being a Delta Force operative and computers. He lives in a fortified house outside of town and watches the world through his monitors. His life forever changes when none other than his FBI contact, Blade, comes to his door. The problem is she is supposed to be a he and she needs his help tracking down a killer.

Abigail Sharpe-code name Blade-is a field agent for the FBI. For two years she has been tracking a serial killer. When several agents are killed because of her, she is suspended, and the case given to another. With no other choice but to solve the crime herself, Abigail enlists the aid of the only man she knows who can help her. 

Between their computer skills and Aaron's military background, she knows they can capture the killer before he finds another victim. Together they follow the clues that lead to the serial killer and a very deadly connection to Abigail. The closer they come to finding the killer the closer the two get to each other.