According to eyewitnesses, Lil Uzi Vert pulled up on rapper SAINt JHN at the Dialogue Cafe in West Hollywood this afternoon and ended up pulling out his gun in the altercation that followed.

Vert jumped out of his Cadillac Escalade to confront JHN when he was eating and things quickly turned physical.  When Vert flashed the handle of his firearm, bystanders began running, fearing a shooting.

By the time the LAPD arrived both rappers were long gone.

SAINt JHN was spotted with Uzi's GF Brittany Byrd a few months back and the early speculation is that's why Uzi went after JHN.

Update:  TMZ reports Byrd was there and things got really ugly:

"The sources say Uzi threw a punch at JHN and missed ... he fell down and his gun fell out on the ground. We're told that's when Brittany got up from the table and approached him and he allegedly pushed the gun into her stomach and allegedly struck her. Everyone left the scene and we're told she going to a hospital and then planning to file a police report."