It was just sloppy writing to end an otherwise good season. Season 4 is the beginning of the end of this show. It's running out of gas.
If Milan were that easy to kill, they should have done it much earlier! An entire lethal crew of Serbians hemmed up by a few dusty-lookin' street nikkas led by Dre! Milan's men see everything, they tried to tell us! Yet, they don't see Dre quickly letting eight nikkas into a side door and move to see what's happening?
Greg was usually shown as a sharp and cunning. Yet, that final scene with Mike had him looking like an amateur! After he got that call confirming that he was the mole, you'd think he would simply play along with the Angela angle Mike was trying to push. The whole idea was to talk to all the people he suspected and build a legitimate case piece-by-piece based on the illegal bug evidence. Yet, there he was cheesing and jumping the gun after he confirmed Mike was the mole, while being in a potentially dangerous one-on-one situation with the mole unarmed!
Did this nikka think he was going to arrest Mike by himself?
Jukebox having a cop car in NYC out of her jurisdiction in DC?
The Lobos Mole investigators simply giving the
and bouncing after Greg was killed. No further probing on their part.
That was about as bad as the lack of questioning or investigation regarding Sean's death.
