Shia LaBeouf Headbutts Man on Street After Calling Him Names, on Video

Shia LaBeouf was apparently looking for a fight before he got his butt kicked early Tuesday ... and we have video of what may have instigated his epic beatdown.

Watch the video ... Shia appears to be talking to a guy on the street, which seems normal ... but for some reason, Shia has his arms tucked inside his T-shirt.

Then, he suddenly starts shouting obscenities at the guy -- an older gentleman who stays cool the whole time -- and lunges forward to deliver a headbutt straight to the guy's face!

And we've got new video above showing a different angle of the scene outside the bar, apparently around the time he gets manhandled in the street before police arrived, and a different view of him being treated by paramedics.

Jeffrey Damnit, a Mardi Gras attendee who was present, tells TMZ ... Shia was at a place called R Bar in the French Quarter around 5 PM yesterday. According to Jeffrey, Shia accidently fell onto him while ordering a jug of water -- he says Shia told him, "You f***ing push me and I'll kick your ass."

Jeffrey left the bar, and he says when he returned around midnight, Shia was still there ... but this time the actor had been kicked out. Jeffrey alleges Shia tried to bite the bar manager, calling him "the F-word" and "chattering his teeth together."

As we reported ... police say witnesses allege Shia punched a bar staff member, left the venue, then later returned, acting even more aggressive.