HYDRA knew their dirty secrets wouldn't stay secret forever. They knew that someone would break into their base, steal their Super Soldiers. So they created failsafes. Helmut Zemo killed the five Super Soldiers in their capsules that day. A bullet in each of their heads. Swift, clean, painless. He didn't know that the opening of HYDRA's tomb triggered the awakening of one last Winter Soldier, ready to unleash decades of anger out on the world.