Mere days after bassist Pete Wentz told a reporter from the Chicago Tribune that rumors of a Fall Out Boy reunion were false, singer Patrick Stump teased the crowd at the band's Monday (Feb. 4) comeback gig. "I told you we were gonna come back! Why didn't you believe me?"

Rolling Stone reports that "the crowd was on the brink of hysteria" when the group took the stage at Chicago's Subterranean club Monday night, strutting out to the strains of 'Thriller' and kicking off a hits-heavy set that included -- 'I Slept With Someone in Fall Out Boy and All I Got Was This Stupid Song Written About Me,' 'A Little Less Sixteen Candles, a Little More 'Touch Me,'' 'Dead on Arrival,' and 'This Ain't a Scene, It's an Arms Race,' as well as "deeper" cuts like 'Honorable Mention' and 'Calm Before the Storm.'

"Today is kind of a big deal for us," joked Stump, referencing the night's festivities as well as the new Fall Out Boy album 'Save Rock N' Roll,' which is due May 7 and was announced Monday morning in a surprise press release. The new single, 'My Songs Know What You Did in the Dark (Light Em Up),' is at No. 2 on the overall iTunes Songs chart, and RS noted that it seemed like everyone in attendance already knew all the words -- a claim you can verify by watching their performance, captured in fan-shot video and embedded above.

All this FOB-related excitement will make it hard for fans to wait until May, but Wentz promised Billboard that the new songs will be worth it. Calling it "the best album we've ever made," he said, "It doesn't sound like the other Fall Out Boy albums, but it sounds exactly like Fall Out Boy in 2013."

Watch Fall Out Boy Perform 'My Songs Know What You Did In The Dark (Light Em Up)'

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