He is heavy-set and has tattoos that cover his shoulders., and takes his nickname by Harry Dresden flattening his nose with a kinetically-boosted punch. According to Parker, Flatnose was never good enough to challenge him, even when younger.
In Fool Moon, he's in the Full Moon Garage with the Streetwolves when Harry Dresden visits. A female in the group, Lana, stirs them up. He blocks Dresden's exit through the only doorway and stands threateningly. Dresden punches him in the nose using one of his kinetic rings for extra power. Flatnose is thrown across the room about six feet.
Later, Flatnose is in the van when they come after Dresden. After Dresden crashes their vehicle, he starts shooting at Dresden. Parker breaks a bone in his gun-holding wrist to stop him. Parker wants to kill Dresden himself. Not long after, Flatnose challenges Parker, saying Lana is right, but is defeated quickly and easily. He is shot to death by the FBI hexenwolves during their battle.