Jack Hunter is an agent with the CIA.
To narrow it down even more, he is an assassin with the Agency. Of course, they would be the first to swear that they were no longer in the assassination business. That had been prohibited by Congress so, of course, they stopped. Except reality showed they still did it and Hunter is the most real thing you can get
We meet Hunter after he had stopped being the finger on the trigger, at least not when the target is a human and the orders came from Langley. He had tired of all the killing and the memories that came with it so he walked away and would have gladly stayed away, contentedly living with a young woman he met after quitting and the little girl she was raising alone. The three made a very happy family; up to the time some sick people did some sick things to the two women he loved. That would bring the killer back in full force.
This return would also get him noticed by his old handler at the CIA, Jeff Hale, and his younger and very determined protegee, Fawn Aspen. She had never heard of Hunter before he began his revenge trail but Hale was more than familiar with him and his impressive and frightening history.
'Praying Mantis' was the name of the Enhanced Operative program he and nearly two dozen others had been in. They had "been trained by the CIA's most sophisticated operative program to be as lethal as it was physically possible to make a man. When rappers said there were six million ways to die, [these guys'] methods were what they were talking about". There had been 8 in the group that Hunter was in but a particularly bloody [operation] in Afghanistan had seen the death of seven of them. Only Hunter remained. After his return, he went AWOL and the program was shut down.
Now that he has resurfaced, Hale, who has a need for his talents, has a way to get the man to 'volunteer' yet again. Hunter had earlier learned the names of three of the powerful leaders who had engaged in the horrific torture and murder of Hunter's family and has already removed them from this life. Hale knows a lot more names.