The Brief: "Shots Fired" is often used an exclamation, following a diss.
It’s sometimes used with hashtag on social media (#shotsfired) and there’s often an implied sarcastic tone.
— bdoggy (@bdoggy6) March 11, 2019
More often than not, it’s usually the person/group who has been insulted that acknowledges the diss with this statement.
How many 'Nice Guys' does it take to screw in a lightbulb? 💡
— Dear Catastrophe Leah (@wilde_thing) March 12, 2019