History
Aaron Heller was in Nazi concentration camps as a prisoner during WWII. In modern times him and his daughter became Nazi hunters, and visited Anna Kapplebaum in the hospital after she fainted from seeing a former Nazi doctor. The pair promised to slay the doctor, and upon returning later, they along with Captain America found Anna had been kidnapped. The trio found and confronted the doctor, which was too much of a strain on his heart and Aaron appeared to have a heart attack, leaving it down to his daughter to pull the trigger.[1]