2003 Chevrolet Impala Replace Rear Passenger Side Window On 03 Impala

I need to replace the rear passenger side window on an 03 impala. There is a triangular piece of moulding in the rear corner of the window frame that needs to be removed to fit the window in. I understand there is a 10mm screw and a clip holding the piece in place. I have removed a screw from the inside of the door but can not see the clip.

What I really want to know is how I disconnect the clip?