See What Happened Before 'Cop of The Year' Pulled Out His Gun and Tackled Teen at Texas Pool Party

Hundreds marched outside Dallas to protest a white police officer who they say used excessive force on a group of black teens at a pool party in Texas.

Protesters took to the streets last night to express outrage over the take-down of a bikini-clad teenager at a pool party in McKinney, Texas.

Hundreds marched through the Dallas suburb to the pool where the incident took place, yelling, "What do we want?," "Justice!" "When do we want it?" "Now!"

WATCH: Texas Crowd Sang National Anthem While Gunfire Exploded in Terrorist Attack

And we're now hearing from the young man who shot the video that has gone viral across the globe.

Brandon Brooks says the day began as a celebration that turned ugly in a hurry.

He told INSIDE EDITION, "We were just having fun. It was the last day of school and everything, and we were, like, dunking each other in the pool. It didn't get too out of hand."

The party was organized by 19-year-old Tatiana Rhodes at a community pool in her neighborhood. She says some of her neighbors started insulting her guests when too many showed up, some apparently uninvited.

Rhodes said, "This lady was saying racial slurs to some friends."

One video shows Rhodes fighting with a woman she says was taunting her.

But, another neighbor claims it was the guests who were out of control.

READ: Cameras Capture Police Throwing 8 Months Pregnant Woman to The Ground, Handcuffing and Arresting Her

Bennet Embry told INSIDE EDITION, "The neighbors did not call the police because there was a big African American party, security called police because they were fighting and people jumping over the fence and things of that nature."

When the police arrived, everyone scattered. Corporal Casebolt, the cop now under fire, tripped and fell as he chased the teenagers, landing in an awkward barrel roll!

That tumble may have sparked his anger.

Brooks added, "It was very scary, especially when the officer pulled his gun out."

Officer Casebolt's heavy-handed tactics are being widely mocked.

Jon Stewart mocked him on The Daily Show, saying, "How do you go from a pool party to this? 'When I say [expletive] Marco, you say Polo!'"

READ: Jon Stewart Gets Serious with New York Mayor Bill de Blasio on 'Daily Show'

Watch Below: 'Officer of the Year' Suspended After Throwing Bikini-Clad Teen to the Ground