The shots fired phrase comes from real police and military radio language for reporting that gunfire has begun, which is why the clip carries instant urgency even in a joke context. Online, that serious meaning was turned into slang for a direct verbal attack, especially in gaming, streaming and meme culture during the 2010s. Short alert sounds like this spread through soundboards and edit packs because they are easy to drop into any timeline. It remains popular as a one-second escalation cue that needs no setup or explanation.