In journalism school, one of the first lessons our indepth journalism professor taught us was to never say "I understand" as a reaction to an interview subject telling you about something tragic...because you dont. What you're supposed to say in response to a lament...either there isn't a uniform response or I don't remember, but just getting to the point and asking questions seemed to work...people don't need to be insulted or patronized when they're feeing grief.