US police officer Eric Casebolt has been placed on leave after a video showed him pushing a 14-year-old girl in a bikini to the ground at a pool party and pointing his gun at other black teens.
The incident began when officers responded on Friday to a report of a disturbance involving a group of young people at a neighbourhood pool in Dallas, Texas.
McKinney Police Chief Greg Conley said the youngsters did not live in the area or have permission to be there.
When officers arrived, residents and private security pointed out the juveniles, who were "fighting and refusing to leave," Conley said.
As officers dispersed the crowd, the 14-year-old girl was "temporarily detained" by an officer, said Mr Conley, who did not describe what led to her detainment.
The video showed Casebolt pulling the girl to the ground then appearing to use his knees to pin her face-down. He can also be seen pointing his gun at other teens and cursing.
Casebolt reportedly said: "Don’t make me f**king run around here with 30lbs of goddam gear on in the sun because you want to screw around out here."
The girl can be heard shouting: "Call my momma."
McKinney Mayor Brian Loughmiller said in a written statement that he was "disturbed and concerned by the incident and actions depicted in the video." He called for the city and police to quickly investigate.
Mr Conley did not identify the officer or the girl. McKinney is an affluent, predominantly white city. Most of the teens seen in the video are black.
Incidents involving white law enforcement and black suspects have raised concerns across the US, in particular since last August when a white police officer fatally shot a black 18-year-old in Ferguson, Missouri, fuelling a nationwide "Black Lives Matter" movement.
Some witnesses told The Dallas Morning News that the police targeted black teens at the pool party.
But Benet Embry, a local radio personality who is black, said the police officer's action was not about race.
"This is not another Ferguson. This is not another Baltimore. This was a teenage party that got out of hand," said Mr Embry, who lives in the neighborhood and said he witnessed the incident.
He said police were right to respond.
"That's what they are supposed to do: protect us," Mr Embry said. "I don't know any other way he could have taken her down or established order."
One man was arrested for interference with the duties of a peace officer and evading arrest, Mr Conley said. Everyone else was released.