A man who got socked in the face by a cop in a viral video argued with police as they tried detaining him ... something we can now see in body cam video.
28-year-old Alexander Mitchell had an ugly run-in with LAPD last month in Watts, CA -- in the South Central area of Los Angeles -- when officers came upon his car, which they say was double parked and facing the wrong direction on the road.
They tapped on the guy's glass trying to figure out what was going on, and soon ... things escalated, as Mitchell tried asking why he was being hassled and demanding a supervisor.
Eventually, the cops get him of the car and they start frisking him for weapons while also trying to get him in handcuffs -- but Mitchell keeps on arguing and you can see tensions start to rise ... which eventually leads to one of the officers dealing him issue a sucker punch.
It's a quick hit -- which could be seen in full in a bystander's video -- and now ... LAPD is catching heat for what many are calling a blatant display of excessive force.
Mitchell was eventually busted for obstruction and resisting arrest -- but he and his loved ones are crying foul. An investigation is underway to see if the cop was justified.