Roland Sand is an agent with the Association.
At least he is when we first meet him and though his situation will change over the short time we know him, his first employer is vital to know in order to understand Sand.
The Association is an unofficial group within the American intelligence community run by a one-eyed man named Bartus Kolinski but called the Bohemian. This man was himself an excellent killer of men, an invisible man that witnesses "looked past and through him but never at him" who was paid by a government slush fund that existed for people like him and his group but which no one would ever admit to knowing. The NSA, the CIA, who knew how many of the alphabets made use of the Association when anonymity was as important as success.
It was the Bohemian who had trained him, molded him, "broke down Sand and built him back again in the image of the Association". This had started 16 years before and in those many years he had performed his duties with precision and skill.
He is called the Quiet Assassin because he is both and excellent at it. He is a patient and silent man who prefers to do his job with little fanfare. And he is a killer.
Sand has a distinctive appearance, thanks to a roadside bomb years earlier on the outskirts of Mosul in Iraq. Because of it he has a scar that "ran crookedly down the left side of his face" which "strangers always stared at", "long and ragged. A slash of white against his tanned skin". The top of his left ear was missing. Some of his skin had melted. Flames had removed most of his hair and the rest he shaved away. A dark mustache and goatee were used by him to hide "as many of the scars as possible". Thanks to that IED, he has few friends anymore and too many bad strong memories of the night he led those under his command into destruction. "The wounds had healed. The guilt suffocated him still."
"It was far easier to hide away in bad weather."
"A man's next thought was never as quick as someone else's last bullet."
Regarding the Bohemian, "it was said ... God had given him a brilliant mind but had forgotten to include either a soul or a conscience."