Short: I have this memory of maybe 8 years ago or longer where an episode ends when a guy essentially walks in to jail kills a dude and walks out.
Long: The episode likely occurred sometime before 2010. All I sort of remember is that the prison guards let this random guy into jail to kill the main "bad guy" in the episode. I feel like the "bad guy either killed a cop, or did something bad like that. I just sort of remember the ending where the dude puts some music on, walks into the prison and kills the guy then walks out. Of course, all the guards allow it to happen.
PLEASE help it is killing me!!!