First, you only have to post the question once.
Second, can you remember anything else about the scene. As in, was it tropical, did it look like it was shot in a studio? Any idea how long ago it aired?
I don't recall anything like this happening in Five-O. Lots of people were shot certainly but I don't remember a guy shooting his mother. There were a few helicopter chases where the drivers were shot at. Season 2, Kiss The Queen Goodbye and Season 9, Double Exposure come to mind right away. But nothing is ringing any bells for what you're looking for.