There is no widely documented original source for this clip, so it is best understood as an internet soundboard creation rather than a line from a film or show. The humour comes from the mismatch: a serious, dramatic gunshot is immediately answered by an ordinary dog bark, which undercuts the tension in seconds. It has circulated mainly through meme edits, short videos and soundboards, where creators reuse short, instantly recognisable effects to signal a joke. Like other gun sounds, it works because listeners recognise the first noise instantly, then get an unexpected animal reaction instead of a dramatic payoff.