The Texas police officer who sparked community outrage when he was captured on a cell phone video slamming a bikini-clad black teen to the ground and pulling a gun on her young unarmed pals has resigned.

Eric Casebolt, 41, resigned a day after a rally was held to demand that he be fired from the suburban McKinney police department. The department promised a thorough investigation and immediately placed the white officer on leave when the video surfaced on social media.

McKinney Police Chief Greg Conley on Tuesday condemned Casebolt's actions as "indefensible" and said the officer had resigned of "his own will" while under investigation and will be allowed to keep his pension and benefits, reports the Dallas Morning News.

"Our policies, our training and our practice do not support his actions," Conley said. "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." He said an investigation will continue to determine if Casebolt should be charged with a crime.

The ugly confrontation occurred when police were called to a disturbance at a daylight pool party in the community about 40 miles north of Dallas. The teens were dressed in swimming clothes, and most sat or lay on the ground, complying with police orders.

When Casebolt began arguing with a young black teen, he threw her to the ground, then pulled his gun on her friends as they rushed toward her to help. Another officer ran up and yanked back Casebolt's gun arm before he holstered the weapon.

Casebolt didn't apologise or make any statement when he resigned, said Conley. "It was just a simple resignation, 'I resign,'" Conley said.

Mayor Brian Loughmiller said the incident is "not indicative of McKinney as a whole," and urged citizens to help the city "move forward in a positive manner."