Based on the context and the answer, generate a question. 

Context: Unfortunately , there is no proof i did n't do it . I was alone for a couple hours , and then Alicia and her friend Greg came over around 2 am and we played Mario on the nintendo until around 5 am .... But they did n't check out Kristen 's window , and therefore did n't know if it was broken before or after they came over . If it was after , i have an alibi , because Alicia spent the night .

Answer:

It was someone we did n't know .



Who might have broken the window ?