The sound comes from The Purge, the 2013 dystopian horror film written and directed by James DeMonaco, where an official broadcast marks the beginning of the annual twelve hour period when almost all crime is legal. The franchise sequels and television series reused the same alert tone, making it the most recognisable audio cue from the series. Clips of the siren spread through trailers, Halloween attractions and social media edits, and it remains popular because viewers instantly connect the wail with danger, lawlessness and a countdown to chaos.