God, that was almost better than sex.
Now, where was I? Oh, yeah: Sam's paralyzed with horror, even though he can't shut up with the screaming for some reason, and Dean arrives precisely in time to yank Sam from the apartment just as the blackening Jessica goes nuclear, wiping out the entire bedroom in the process.
After the glorious flames finally fade to black, we get a scene that parallels the one at the top of the hour, with the firemen and the EMTs and the cops and the rubberneckers and such. Dean stands near a squad car, watching the last of the smoke billow from his brother's apartment before turning to join Sam down the street at the Impala. He finds his younger brother determinedly and expertly loading shells into a double-barreled shotgun. Dean wordlessly searches Sam's impassive expression for some clue as to what's going through Sam's head at the moment. By way of response, Sam tosses the shotgun into the trunk, and as the shot cuts to TrunkCam, Sam simply announces, "We've got work to do," before slamming the thing shut.
Yeah, that was a hell of a cheesy ending, but did you hear me? They killed Joey Potter, people!