Last night's (June 11) Spin event in Chicago wasn't a scene. It was a goddamn bar fight. Following their sold-out Charter One Pavilion show, Fall Out Boy played a special acoustic set for a packed house at the intimate Schubas venue, but only to be met by a surly heckler up front.

According to Spin staff present at the exclusive gig, a patron who bartended the pre-show gathering, began heckling Wentz prior to the band's final song. Shrugging the insults off in good fun, the mega star bassist delivered a few one-liners of his own. But in the moments that followed, Wentz was met with snatching fists from the aggressive concertgoer as the band headed back towards security. While Spin staff maintains that there was no wrong-doing on Wentz's part, the FOB poster boy retaliated with one punch in self-defense, while leaving the rest of the dirty work up to his body guards. Known for energetic live shows, it was no surprise that the band still delivered a rousing rock set, a la unplugged. Before lead singer Patrick Stump could finish the opening line of the first song "This Ain't a Scene, It's an Arms Race," the hometown crowd erupted and sang along for the remainder of the tune. Before beginning their second song Wentz clarified, "I'm Like a Lawyer with the Way I'm Always Trying to Get You Off (Me & You)" isn't about a girl "it's actually a love song about Chicago." After jokingly asking the crowd "Where's Ashlee?" referring to his girlfriend Ashlee Simpson, Wentz looked into the crowd and visibly strained to hear something… "A dude from Wilmette [IL] just called me a sell-out," he laughed. Finishing with a cover of Michael Jackson's "Beat It" and "Sugar We're Going Down," the set was short, stylish, sweet and over.

Pete Wentz then thanked the slightly crammed crowd at Schubas. Patrick Stump and Andy Hurley trailed and the bandmates exited the stage, but almost as a last minute side note guitarist Joe Trohman stayed behind, grabbed a microphone and added "danke schoen” -- and with that said, anarchy arose.

Following Trohman's German "thanks," the crowd abruptly started moving away from the stage. Afterwards, shards of glass, blood, at least one visibly injured man and a confused mob lay across the Schubas floor. Unfortunately, that's where the information ends. Chicago Police cleared the crowd before details could unfold among the mass.ANGIE MALDONADO / PHOTOS BY KAREN CHAN

We asked: If you could have Fall Out Boy take a line from a movie use it in a song, what would it be?

Name: Martise Cooks
Age: 22
Hometown: Chicago, IL
Occupation: Office manager
"'Hasta la vista baby!' -- Terminator 2: Judgment Day."

Name: Bobby Irons
Age: 24
Hometown: Chicago, IL
Occupation: Schubas employee
"'You taste like a burger. I don't like you anymore.' -- Wet Hot American Summer."

Name: Jane Anderson
Age: 21
Hometown: Minneapolis, MN
Occupation: Student
"'Do I make you horny, baby, yeah, do I?' -- Austin Powers"

Name: Jessica Cohn
Age: 23
Hometown: Chicago, IL
Occupation: Educational administrator
"'Three horns never play with long necks' -- The Land Before Time."

Name: Tanya Martinez
Age: 24
Hometown: Chicago, IL
Occupation: Student
"'What do you want me to do dress in drag and do the hula?' -- The Lion King."

Name: Jonathan Regmier
Age: 21
Hometown: Chicago, IL
Occupation: Advertising
"'Is butter a carb?' -- Mean Girls."

Calm before the storm, Fall Out Boy performs in Chicago / Photo by Karen Chan

Bassist Pete Wentz / Photo by Karen Chan

Lead Vocalist Patrick Stump / Photo by Karen Chan