John Kane is a freelance assassin.
That's what he has been doing for a couple of years now, operating more or less out of Atlanta. Kane would take only the cases that interested him but when he toke one on, he saw it to the end and that end was usually final for someone. Kane was very, very good at dispatching people, especially when they deserved it and deserving it was the deciding factor as to whether Kane would accept the job.
The jobs came to him via his broker, Jackson Carter, CPA. At least Certified Public Accountant is what the lettering on the door says but as his secretary and receptionist, Sarah, could tell you, she is instructed to turn away any new business with a friendly "no new clients at this time". And she might admit that there have been no old clients for the two years she has worked there. Carter was really the sort of man that someone who knows someone who knows someone would be contacted when there was a special sort of work needing doing. And Kane was the man that Carter would often call to do it.
But Kane had not always been Kane. Before, he was Cain, a codename for the man he had once been. Edward Starke, born about 35 years before the first recorded adventure. Raised in Virginia with a good family life, attended college on a football scholarship until an injury ended that. Denied military service because of that injury. Then while working at a gun store, came to the attention of Whistler.
Whistler was a big wig with the Agency. He saw in Starke a talent for killing and looked further into him. Eventually a job offer was made and after the requisite training, Starke became Cain and then followed several years of solid service. Then the explosion, the physical and mental trauma that would alter him. But he knew too much. In some circumstances, he might be marked for elimination but Whistler chose not. What Kane was given, unknown to him, was a second choice.
Chemically induced amnesia, followed by sessions to "give" him a new identity with a past of its own that did not include the Agency. Now named John Kane, he was put out on the street but monitored. His new history had him with a different but still happy childhood, service in the Army, a good past.
But when someone has been trained and trained to be a killer and had killed on numerous occasions as part of his 'normal' life, can that be forgotten? The answer is no. So Starke became Cain the government killer who became Kane the contract killer.