The phrase itself is plain French and translates literally, which is the core of the joke that has kept the clip circulating on soundboards and in meme edits. Its exact film source is not widely documented, so it survives mainly as a standalone reaction line rather than as a famous scene quote. Shared in French-speaking communities first, it crossed over because the tone alone signals the gag even to listeners who do not speak French, and it is now reused whenever an outcome is painfully predictable.
About this sound
French movie line 'Assassiné, il en est mort' delivered deadpan, used as a meme reaction for obvious deaths, fails and dramatic overstatements online.
This short clip captures a flat, matter-of-fact French delivery of the line Assassiné, il en est mort, which translates to assassinated, he died from it. The humor comes from the redundancy, stating a fatal outcome as if it were a surprising extra detail. The voice is dry and serious, with no music or effects underneath, which makes the obviousness land even harder. It works like a caption spoken aloud, turning a dramatic death or a total failure into a deadpan punchline that needs no explanation.