A white police officer in the US has resigned days after a video was posted online showing his treatment of a group of teenagers, many of whom were black.
Officials said Corporal Eric Casebolt, 41, submitted his resignation "on his own will".
In a video - filmed on Friday (local time) in McKinney, Texas - Corporal Casebolt, who is white, is seen pinning 15-year-old Dajerria Becton to the ground with his knees.
Police said he was responding to disturbance reports at a pool party.
Corporal Casebolt was placed on administrative leave following the incident.
Hundreds of people later marched at the scene, demanding that the corporal be dismissed.
'Out of control'
At a news conference today, McKinney police chief Greg Conley described Corporal Casebolt's actions as "indefensible".
"Our policies, our training, our practice, do not support his actions. He came into the call out of control and as the video shows, was out of control during the incident.
"I had 12 officers on the scene and 11 of them performed according to their training. They did an excellent job."
Mr Conley added that the authorities were continuing their investigation of Friday's incident.
In the video, which is more than seven minutes long, Corporal Casebolt is shown swearing at a number of black youths, pointing his gun at others, and pulling the girl by her arm, before pinning her to the ground with his knees.
"Call my momma!" the girl screams several times as she struggles with the officer.
Dajerria Becton later told the Texan broadcaster KDFW: "Him getting fired isn't enough."
In a statement posted on Facebook, police said they were called because a number of uninvited people refused to leave the swimming pool.
A fight then broke out, and more calls were made to police.
On Monday night (local time), close to 800 people marched through McKinney, a city of almost 150,000 people.
They walked from a school to the swimming pool, carrying placards with slogans including "My skin colour is not a crime" and "Don't tread on our kids".
Civil rights leaders in McKinney said they wanted an investigation by the US Justice Department.
However, some local residents defended the policeman's actions.
Corporal Casebolt resigned after almost 10 years of service.
The incident comes at a time of heightened scrutiny about how US police forces respond to minorities.
Protests have followed the deaths of several African Americans in police incidents since July 2014 - Michael Brown in Ferguson, Missouri; Eric Garner in New York; Freddie Gray in Baltimore; and Tamir Rice in Cleveland, Ohio.