I am sure if you are any type of fan you have seen or heard about the very epic spoilers that came out from filming a bit before that & I am not at this time going to speculate on what I think they mean... but I do have theories.
Instead, I am simply going to post the photos from this evening of filming & give what few details I could put together from it.
There was two sets of scenes this evening. Some inside the historic Oprheum Theatre (you may recognize it as the place that season 2 ended in). The scenes were from what I heard from extras & crew were to do with an explosion/bomb going off at the symphony. On set for those scenes (may not actually be in all or any scenes... were just seen on set) Anna Torv, Joshua Jackson, Emily Meade & Brad Dourif....as well as many extras in some very well done make up/special fx. The scenes appear to be set in the alt-world, as I saw several members in "Fringe unit" gear.
The later scene, which the public did see included a landscape of scattered debris, including part of the Orpheum sign laying on the ground burning as burned out cars filled the street, Torv & Jackson arrive & walk up towards the disaster zone. Josh was wearing an army style jacket with the name plate "Bishop" on it & a "Fringe" badge around his neck. My impression of the way both characters were dressed is this is to potray them in the future at some point as both Torv & Jackson had different hairsyles than the way they usually have them when playing Agent Olivia Dunham (or Fauxlivia either) and Peter Bishop.
I am not certain....but I did notice a telling spoiler in the pics I took. I wont speculate on it anymore till I have a chance to confirm what I saw. I tried avoiding posting pics involving this potential spoiler.
Anyways, below is a few pics from the day