The action at SoFi Stadium didn't end with the final whistle of the Rams vs. Bills game on Thursday night -- because some of the two teams' fans got into a wild brawl in the streets surrounding the venue afterward ... just feet in front of ex-NFL star LeSean McCoy!
Former Philadelphia Eagles linebacker Emmanuel Acho captured the scene on video and posted it to his social media page ... showing two L.A. fans getting into it with a man in a Stefon Diggs jersey.
In the clip, you can see the Diggs supporter threw a punch at a guy wearing a Cooper Kupp shirt -- and then all hell broke loose.
A man in a Cam Akers jersey raced in to try to get a piece of the Bills backer -- before he slipped and nearly ate a couple of punches.
Eventually, a police officer ran in and grabbed one of the men, which appeared to end the altercation.
McCoy and Acho were standing right behind the fracas the whole time -- commenting on it all as it was going down.
"They can't fight!" said McCoy, a former Bills running back.
No word if any arrests were made -- we've reached out to cops, but haven't heard back yet.
As for the game, the Rams were blasted in the NFL's season opener, 31-10 ... making it a REALLY rough night for the Kupp and Akers fans.