Oeznik, Zemo's butler
This person is Oeznik, Zemo's butler, that we had previously met in episode 3, "Power Broker", when Zemo takes them to his private plane. Compare the images below from the two scenes:
It is also hinted at a that Zemo is behind it even if you don't recognise the character. Right after the close on Oeznik it cuts to a view of Zemo in his cell at the Raft indicating he is somehow related to the incident. We also have Valentina's comments to Olivia, Walker's wife, on the incident. She jokes she was behind it but it seems to be just that, a joke.
Valentina: Oh! Ooh. Hey, Walker, check your phone. Looks like our friend, Zemo, kinda got the last laugh, right?
Valentina: Couldn’t have worked better if I planned it myself. Oh. Well, maybe I did. No, I’m kidding, I didn’t. Or did I? Anyway, it’s gonna save people a lot of paperwork and a lot of redacting and a lot of shredding.
The Falcon and the Winter Soldier, Season 1 Episode 6, "One World, One People"
Lastly, it of course makes sense that Zemo is behind it given his devotion to getting rid of the super soldiers and an Avengers-like team. Zemo's mission throughout the season is to destroy the super soldiers and the serum's creator. It makes sense that he contacted Oeznik at some point to help put an end to them should he be captured.
Zemo: I spent years hunting people HYDRA recruited to recreate the serum. Because once it's out there, someone can create an army of people... like the Avengers. I ended the Winter Soldier program once before. I have no intention to leave my work unfinished.
The Falcon and the Winter Soldier, Season 1 Episode 3, "Power Broker"