MM, yours just about sounds right in understanding what I'm reading. A man returned for his high school football coach's funeral, and dropped by his ex-girl friend's, wanting to apologize for what he did to her and wanting her to show her true feelings.
"Oh, get a life! And grow up while you are at it. You're not the football hero anymore."
Actually, Mr. M. is right. You can "fire with both barrels" or "unload with both barrels" figuratively. She's not shooting at him with bullets, but with words. She tells him to "get a life" and "grow up" and reminds him he's not the star he was in high school - those are all pretty hard things for him to hear and (depending on the context, but it sounds like it here) rather harsh things to say.