Near the end of LOTR: Two Towers when Faramir is close to taking the ring back to Gondor, Sam pleads with Faramir not to take the ring by saying something like this:
"Do you want to know what happened to Boromir? You want to know why your brother died? He tried to take the Ring from Frodo"
How would Sam know this at all? Earlier in the film it was shown that Frodo didn't even know Boromir had died. Frodo and Boromir were all alone when Boromir tried to take the ring so how could Sam have known Boromir tried to take it and that it led to his death?