Interrogate his girlfriend as though she were a criminal, of course ....
http://www.theguardian.com/us-news/2014/dec/14/john-crawford-girlfriend-questioned-walmart-police-shot-dead?CMP=share_btn_tw
http://www.theguardian.com/us-news/2014/dec/14/john-crawford-girlfriend-questioned-walmart-police-shot-dead?CMP=share_btn_tw