Yup. Even before Steve asked about the mission, when he found out about Hydra's involvement in Howard Stark's death, Bucky was literally shown on the screen as a top assassin a second before the "accidents happen" part showed Howard's dead body. That fits amazingly with Steve's reaction when he was asked by Tony if he knew. He first says he didn't know it was Buck, because he only knew it was implied by Zola that it was Buck, but when pressed by Tony, he had to come clean and stop hiding behind the fact that it was implied. He knew from the point of that video that his friend was the one that completted the hit, and from that point on he hid his knowledge from Tony. Steve would have gotten official confirmation once he and Sam asked Bucky about the mission from that night. It's pretty cool how strong it all matches up. Impressive long term storytelling that doesn't hold your hand.@gluvnast doesn't understand the difference between Cap knowing that Bucky killed Tony's parents, and Cap knowing there existed footage of this. Cap might not have known that a tape existed but he had known since The Winter Soldier that Hydra was behind the death of Tony's parents. After Cap and Falcon get a hold of Bucky, Cap asks him what Zemo wanted to know, which were the details of his mission killing Tony's parents. If you can't fill in the gaps from there (Bucky tells Cap and thus Cap knows), then sorry breh, you might wanna stick to watching Christopher Nolan movies were every plot detail is being explained to you in a five minute speech.
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