The police video that shocked America

A video of a black teenage girl being dragged to the ground by a white police officer is being widely shared online, and has become the latest talking point in the debate over police and race relations in America.

"Sir, we just came for a birthday party - please sir," says one teenager who's been ordered to sit on the ground. The video, shot Friday evening in McKinney, Texas, a city about an hour away from Dallas, shows a confrontation between a group of teenagers and two police officers.

But the pleas don't placate one of the officers who's seen shouting and ordering a group of girls around. He wrestles one of the girls to the ground, pinning her down with his knees. He also pulls his gun.

The incident seems to have tapped into the ongoing debate over race and police brutality in America - the 7 1/2 minute video has been watched millions of times, including 10 million views on Facebook and nearly three million on just one of many versions on YouTube.

In a press conference posted to YouTube on Sunday, McKinney Police Chief Greg Conley said the officer shown handcuffing the teenager has been placed on administrative leave and promised an investigation into the incident.

The 14-year-old girl who was seen being wrestled to the ground was temporarily detained but released to her parents, and another adult male was arrested for allegedly interfering with police officers and evading arrest, Conley said. In a statement posted on Facebook, police said they were initially called to the scene because of "a disturbance involving multiple juveniles at the location, who do not live in the area or have permission to be there, refusing to leave".

The video doesn't show what happened before the police arrived, but another video was circulating online of a white adult female fighting with a black teenage girl - while it appears to be related to the incident, there's very little context included.

Since the video really went viral on Sunday, "McKinney" has been mentioned more than 600,000 times on Twitter. More than 30,000 tweets have used the hashtag #BlackLivesMatter, which as BBC Trending has reported in the past, regularly trends after reports of police violence against African-Americans.

A number of prominent #BlackLivesMatter protesters were tweeting about the incident, and one of the most retweeted messages came from activist Deray McKesson: "There were 'too many black' kids at a party. Officers arrive. America." Others were comparing the video with pictures of a biker gang shoot-out in Waco, Texas, last month.

"There are no excuses, the actions of your department are a disgrace to law enforcement everywhere," commented one person on the McKinney Police Department Facebook page. But others defended the police: "This incident should serve as a lesson to all teens in the USA. This McKinney cop just showed how to control a crowd of teenagers."

#BlackLivesMatters activists on Twitter were certain that the officer's action was racially motivated, but in McKinney the racial dimension of the incident was a matter for debate. During Sunday's police press conference, one questioner stated that the video was just one of a series of events where African-Americans were unfairly treated by police (Conley, the police chief, declined to comment). But Benét Embry, a black man who identified himself as a local resident, said on Facebook: "Look, I LIVE in this community and this ENTIRE incident is NOT racial at all. A few THUGS spoiled a COMMUNITY event by fighting, jumping over fences into a PRIVATE pool, harassing and damaging property. Not EVERYTHING is about RACE."