By Jon Herskovitz

AUSTIN, Texas (Reuters) - Austin's police department has launched an investigation into a traffic stop last year in which a white officer twice threw a black woman to the ground and another white officer later told her African-Americans have "violent tendencies."

Art Acevedo, the police chief in the Texas capital, said his department was looking into the June 2015 incident involving a 26-year-old school teacher, caught on police car videos that were broadcast by a local television station on Thursday night.

It is another in a series of incidents caught on video that have raised questions about racial bias in American policing.

Acevedo told local media on Friday that "your heart sinks" when you see such an incident, and that while the woman resisted, the officers did not respond properly.

Police killings of two black men in Louisiana and Minnesota this month triggered protests in various U.S. cities, and two black gunmen upset by those incidents later shot dead five policemen in Dallas and three in Baton Rouge, Louisiana.

The videos of the Austin incident involving schoolteacher Breaion King were released by Austin police following an investigation by the Austin American-Statesman newspaper and local television station KVUE.

King, who did not initially press charges against the officers, told local media she waited to revisit the incident because she was embarrassed and afraid. She has hired a lawyer, who sought the videos, and has not said if she will file a civil lawsuit.

The two officers have been placed on non-law enforcement duty during the investigation.

The Travis County district attorney's office is considering taking the case to a grand jury, the newspaper reported. The office was not immediately available for comment.

In one video, officer Bryan Richter is shown pulling over King for going 50 miles per hour (80 kph) in a 35 mph (56 kph) zone. King is seen stepping out of the car, goes back in to get her driver's license and is told by Richter to put her feet in the car so he can shut the door.

A few seconds later, he asks her to stand up, and grabs her. She is heard saying, "Oh my God," and the officer says, "Stop resisting," as the two struggle.

He then is seen pulling King out and throwing her to the ground. She stands up with her hands behind her back and is thrown to the ground again and the two again struggle.

Later, as King is transported to jail by another officer, Patrick Spradlin, video shows King telling the officer she believes police can be biased against black people.

"I can give you a really good idea why it might be that way. Violent tendencies. And I want you to think about that," the officer responds.

(Editing by Jeffrey Benkoe and Will Dunham)