Young Brock Rumlow led the Savage Crims gang on New York's lower east side. After he brutalized fifteen year old Rachel Leighton, two of her brothers assaulted Brock; the elder of whom was killed. Rumlow fled, entering theTaskmaster's school for criminals, and within three years he became an instructor there under the name Bingo Brock

Martial Arts: Crossbones is one of the world's best hand-to-hand combatants, with extensive training in street-fighting, military combat, and various forms of martial arts, he has trained extensively with the Taskmaster to the point where he was actually made an instructor at the Taskmaster's school for criminals. 

Marksmanship: Crossbones is also a superior marksman with guns, crossbows, and throwing knives.

Interrogation/Torture: He also has some experience with torture and brainwashing, having effectively "reprogrammed" Sin and nearly so with Diamondback.

Pilot: He is also an expert pilot.