Matt Hunter is an agent with the CIA.
Was, actually. He had retired from the Agency when we first meet him though this highly decorated and well respected operative is only around 45 years old on that initial meeting. He had decided enough was enough of the mayhem that he was continually asked to take part in and had moved to a very rustic small house in a swampy region along the Gulf of Mexico.
He would have certainly stayed there a lot longer than he actually did, even after he was asked to return to service to help hunt for a band of terrorists invading the country, except that those very same mercenary/terrorists decided to take him out before he changed his mind. Killing a very good friend and blowing up his simple home with him still in it - that sort of thing tends to anger men like Hunter so he rethinks his rejection of the help request. Not good planning on the bad guys' part.
We will not learn a whole lot about this solitary man during the two adventures we have of him. This is largely because the people telling us about him do not have a lot to divulge, other than he can get riled, not scared, when he is attacked by seemingly impossible odds.
We know he is single though he is not immune to a lady's smile. He is extremely fit and no stranger to hard work. And he is one highly trained and very capable fighter who is confident with his abilities with just his hands and legs as well as when holding, well, virtually any weapon made.
In the second adventure, there is some apparent discrepancy when we are told he retired from the Secret Service, not the CIA. Why the change is unknown though a bit confusing. What is not in doubt, however, is that regardless of his real previous employment status, he remains one very dangerous fellow.