Everyone gets out of their vehicles and starts firing back or setting up the wormhole device. Things aren't so hectic that Walter can't gleefully point out the coolness of a shot Observer slowly floating up into the sky, though.
Dontember fires up the wormhole with the cube and Walter lets loose one of the beacons from the electromagnet, and it fires through the hole like a bullet. "Now, Walter!" yells Dontember, and Walter yells for someone to get the boy, although he likely didn't mean Windmark, which is what's happening. That cranky old bastard smashes through the window of the van to get Michael. Peter tackles him and he pops out -- with Michael and Peter -- and pops back in again close by and then proceeds to beat the ever-loving shit out of Peter, who no longer has any special Observer-shootin' guns. Bet you're missing that Observer neck tech now, stubbly!
Luckily, Peter's got backup. Astrid shoots one of the HenchObservers who show up to help Windmark, but Windmark is too quick for Olivia and now it's her turn for a beatdown. Windmark knocks her to the ground and then lifts her up by the throat, before tossing her aside and turning to go for Michael. Your guess is as good as mine as to why he didn't, you know, kill her, but it's not a mistake he'll live long enough to regret much. Olivia slowly gets to her feet, as the nearby lights shut down and the skyline goes black. Ooh, she's going to go all Carrie on his ass! Windmark, buddy? Unless you've got a maneuver a little more useful than the curious headtilt, then you're -- nope, he's gone. A bloody smear on a truck window, left there after Olivia throws a fucking SUV at him.
Michael takes it all in, and puts his finger to his lips again, looking at Olivia. You know, kid, maybe try WRITING SOME OF THIS DOWN. I mean, if your plan was to get caught so A) The Loyalists wouldn't search the train the fugitives were on or B) So Olivia could get all Cortexiphaned up for this (or both), a little advance notice might have prevented a lot of confusion.
So Dontember hustles Michael over to the wormhole, only to get shot. And not even on purpose, just the spray from a Loyalist's gun as he goes down. Michael sits down next to the body of his dying dad and pulls out the music box and starts playing "What Child Is This" and I know this is supposed to be poignant but YOU'RE IN THE MIDDLE OF A BATTLEFIELD, and at this point maybe the whole friggin' Fringe team should think about accompanying Michael into the future because it's going to require a group effort to keep this kid from getting killed.