Gary Scott Thompson
says the decision to bid adieu to both
came so last-minute that Friday's season-ender - which boasts an explosion and a shooting, to name but two big events, and was purposely designed to coerce NBC into greenlighting a fifth season - not only might
pave the way for Ed's and Mary's exits, but actually has the writers in a bit of a pickle. "The season finale had already been written," Thompson tells TVGuide.com, "so it's going to be challenging to get us out of the situation I put us in."
For Thompson's latest take on why Caan is leaving
, see the fresh