Dr. Aaron Carpenter was the world's greatest living brain surgeon. He knew Bruce Banner from high school, whom he saw as an "insufferable geek."

After Bruce Banner was shot in the head, Carpenter was contacted by the Ancient Order of the Shield,^[1] disguised as S.H.I.E.L.D., the ones who secretly had Banner shot, and was brought in to operate on him. During the surgery, Carpenter was ordered to place a device capable of controlling the Hulk's transformations in Banner's brain. Aaron hesitated, and thought of killing Banner to prevent the agency from controlling Hulk, in order to save lives.