Tarek El Moussa Violently Beat Man in Las Vegas Casino Brawl, Police Say

We're learning more about Tarek El Moussa's alleged beatdown of another man inside a Las Vegas casino -- and the details are truly shocking, 'cause the victim allegedly got pulverized!

According to a Las Vegas Metropolitan PD report, obtained by TMZ ... the HGTV "Flip or Flop" star got into a knock-down, drag-out fight with the man near a roulette table at The Palazzo at the Venetian hotel -- and it was all caught on surveillance video.

The report states ... last Thursday's battle royal was triggered by Tarek's adversary apparently bumping into the chair occupied by El Moussa's dad at the roulette table.

Tarek's father allegedly got upset and turned around to stare at the man before going back to his game. Cops say the man patted the right shoulder of Tarek's dad and said something to him, sparking the violent confrontation with Tarek.

Tarek, who was seated nearby, sprang to his feet and charged at the man, pushing him back before the two got into a "fighting stance."

Cops say the man went for Tarek's legs to try to take him down ... but El Moussa kneed him to the floor. Tarek then allegedly mounted the man's back and pummeled him with three blows to the head. After that, Tarek got up and walked away.

Officers responded to a call of an "assault/battery" and spoke with the victim, who suffered injuries -- namely purple and red bruises under the right eye and a cut on the bridge of his nose.

The alleged victim initially told cops a slightly different story than they saw in the surveillance video -- claiming he was just sitting at the roulette table when someone aggressively approached him and assaulted him as he tried defending himself. He seemingly left out the part about the two men squaring up before he allegedly got beaten up. The victim also told cops he wanted to press charges.

Police also interviewed Tarek, who said he confronted the victim to "protect his Dad due to him having back problems." Tarek then clammed up after police read him his Miranda rights.

As we reported ... Tarek was not arrested ... but he received a citation for battery.