The Kid Laroi ' s crew was involved in a recent brutal bar fight ... and we've learned it was security-on-security violence.

Here's the deal ... Kid dropped by The Pint bar in Nova Scotia after performing at Magnetic World in Halifax on Sunday night ... and that's pretty much right when the mess started.

See for yourself ... Kid Laroi’s security throws a wicked punch at a man who he'd been jawing with ... and TMZ is told that dude was an off-duty security guard who was taking pics of KL and got his phone swiped by Kid's manager. TMZ.com

It doesn't take long for more fists to start flying -- and total chaos erupts! It's pretty savage to watch ... 'cause some punches land big time as more of the crowd jumped into the mix.

It's worth noting ... it appears Kid tried to get in betwee

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