The Ataris -- Singer ATTACKS Drummer ... On Stage

Crazy moment at The Ataris concert in Jersey this weekend ... when the lead singer FLIPPED OUT and attacked his drummer ... firing his guitar at the guy and then throwing the drum kit off the stage.

It was a pretty glorious meltdown ... the band -- famous for their 2003 hit "Boys of Summer" -- was in the middle of a song when singer Kris Roe decided he HATED the way the drummer was playing.

Roe finally reaches his breaking point ... unstrapping his guitar and launching it at the drummer.

When the drummer continued to play, Roe grabbed pieces of the drum set ... lifted them over his head ... and threw them off the stage, until the drummer got the message.

Roe then went to the mic and tried to explain himself -- "Our drummer is f**king failing it tonight ... I don't know what his f**king problem is ... but I'm gonna finish the set by myself."

He added, "It's f**king embarrassing ... I can't handle it."

"I apologize ... but there's a certain amount of f**king sh*t I can take ... hopefully you guys understand ... sh*t happens."

2:04 PM PT -- Kris -- along with the rest of the band (sans drummer) -- has issued a video statement explaining why he flipped out on stage.

Kris says the drummer had been drinking heavily before the show ... "for like 6 hours probably" ... and was a mess on stage, missing beats and playing like crap.

Kris says he would have liked to have handled the situation differently ... "but c'mon ... it's rock 'n roll."

**WARNING -- THERE IS A LOT OF CUSSING IN THIS STATEMENT**