Factual error: Chuck and Penny are seen drinking Rolling Rock beer in clear glass bottles. But Rolling Rock beer has always come in green glass bottles.
Factual error: In the first shot in Helsinki, there is a yellow 4-door saloon car in the right background. It's too far away to identify it precisely, but it's about a 1980 model, something like a Ford Taunus or Toyota Carina - this scene is set in 1957.
Factual error: In a shot in which Barris is on the phone in the sixties, the phone has a modern plug on the handset.
Answer: He was presumably shot by the double agent. Which is why he tells Barry 'It's up to you now.'