Thank you very much for the comment! Beor's death was Finrod's first encounter with mortality of a friend, so I think he would have quite taken aback by it, first realizing the value of time that he, as an immortal, had an eternity of. Even today, many people take time for granted, and then regret how they spent it (or how they didn't spend it), but as an Elf, Finrod was not prepared for that.