In cases when you ask who does something, there are two ways in French:
Who ... ?
Qui means who but there is a longer form in which qui appears twice: qui est-ce qui ...? (literally: who is it who...).
ATTENTION:
You can also sometimes encounter the form c'est qui qui, however, this is NOT a grammatically correct form to use!
See also Questions: Qui / qui est-ce que = Whom ?
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