The acoustic Fall Out Boy set at Schubas last night (following their headlining set for the Honda Civic Tour at Charter One Pavilion) was supposed to be a mellow affair. And it started out as such. The band took the stage a little late, but everyone seemed pretty grooved out on the unplugged rendition of “This Ain’t a Scene, It’s an Arms Race.” Personally, I thought without their overdrive pedals that they sounded even more like Maroon 5, but they weren’t just playing for me.

After “Arms Race” some heckler yelled out, “Where’s Ashlee?” The band sort of shrugged it off, one of them cracking a lame joke about how hard that girl is to keep track of. Then someone in the crowd said something I didn’t catch, to which Wentz replied, “Did a dude from Wilmette just call me a sell-out?”

The night started to acquire a distinctly weird edge. The crowd was giving off some unexpectedly bad energy, and the band looked like they knew it. They played “Beat It,” and the crowd went a little nuts. They followed it up with “Sugar We’re Going Down,” and then everything blew up. I looked down to write something in my notebook and all of a sudden the floor started rumbling. I looked up, the stage was clear, and a tangle of bodies was swerving around the floor. A voice came over the PA telling everyone to leave immediately, that the bar was now closed, even before the fight was done.

Either someone pushed the heckling a bit too far or someone took something a little too personally—I’m not exactly sure what happened. I didn’t actually see Wentz in the mix, but I was told he was full-on part of the brawl. I did see a girl who’d gotten tangled up in it, and she didn’t look so good. The girls from who were there to cover the event seemed confused and bummed out, unsure of how to handle the situation. Personally, I thought it was okay. I had only wanted to see a couple of songs anyway.