In Captain America: Civil War, Bucky informed Cap that there are other Winter Soldiers or super soldiers. My question is what actually happened in the scene in which the other Winter Soldiers started attacking the doctors and guards?
The other Winter Soldiers were being trained, by pitting them against Bucky, but it's clear they were nowhere near as tractable. When the doctor attempted to examine the soldier after the fight, he reacted (seemingly on instinct) and killed him. The rest of the soldiers then began attacking the guards, though it doesn't appear they were trying to escape. It appears they were merely venting their aggression at the nearest targets.
Given that all five of the subjects were in suspended animation in Siberia 20+ years later, we can assume that HYDRA figured out how to get them back under control at some point in the future. But when Steve asks Bucky if Zemo can control them, his response is something like "close enough", which implies that even now the control over these other soldiers is not as complete as his own.