Stopped by police for going 15mph over the speed limit, Breaion King pulled into a fast-food joint’s parking lot. Within a minute of an officer asking to see her driver’s license, the schoolteacher was dragged out of her car and thrown to the ground.

“Put your hands behind your back! You are under arrest!” officer Bryan Richter yells, in video footage published on Thursday. He tells her to “stop resisting!” and struggles to force her down as she wails and cries: “Oh my God, why are you doing this to me?”

Later, handcuffed in the back of a vehicle as she is driven to jail, King has a conversation about racism with another white officer, Patrick Spradlin.

“Let me ask you this, why are so many people afraid of black people?” he asks. “I can give you a really good idea of why it might be that way: violent tendencies.”

He continues: “I’m not saying anything, I’m not saying it’s true, I’m not saying that I can prove it or nothing, but 99% of the time, when you hear about something like that, it is the black community that’s being violent. That’s why a lot of the white people are afraid and I don’t blame them. Some of them because of their appearance and whatnot, some of them are very intimidating.”

Video of the June 2015 encounter was published on Thursday by the Austin American-Statesman and KVUE local news, amid a heightened nationwide climate of concern and anger about aggressive and sometimes lethal interactions between police and African Americans. Fatal shootings by officers in Baton Rouge and St Paul in recent weeks were followed by murderous attacks on police in the Louisiana city and Dallas.

Art Acevedo, the Austin police chief, apologised to King on Thursday and pledged thorough investigations. At a news conference he said both officers had been placed on desk duty, that he was not aware of the video until this week and that King did not file a complaint. Her resisting arrest charge was dismissed in January.

Acevedo told KVUE on Friday he was angry, “sickened” and “saddened” by the footage and that a criminal investigation into the arresting officer’s conduct will take place, as well as a performance review and an examination of the department’s procedures and training.

“There’s a lot of issues in terms of race relations and a lot of issues in terms of race and socioeconomic standing in this nation and we’re not immune from it as a profession,” he said. “We all need to admit that. Every segment of society is touched by this issue and we need to get to work and admit it or we’ll never get through it and past it.”

Police said Richter has been an officer since 2010 and Spradlin since 2001. Acevedo said he reviewed the video on Wednesday with black community leaders for nearly three hours. He said the leaders included Fatima Mann, an activist with the Austin Justice Coalition, who told reporters outside the police station she did not understand how no one in the department had previously raised concerns about the video.

“If that was a white woman, would he have yanked her out … and slammed her on the ground? Most of us could say absolutely not,” Mann said. “For some strange reason, when people look like me, we’re more of a threat, and that means we get treated and thrown around as if we don’t matter.”

The Austin police union said in a statement that Spradlin’s comments were “wrong and not reflective of the values and beliefs of the men and women who serve this community”.

King, 26, told the Statesman she has “become fearful to live my life. I would rather stay home. I’ve become afraid of the people who are supposed to protect me and take care of me.”

On Friday she told the newspaper she appreciated Acevedo’s apology and the incident “is an opportunity to make things better and to change things for the better”.

The footage was made public a day after the release of video from Florida showing the moments before a policeman shot an unarmed black man who was lying on his back with his hands in the air.

Earlier on Thursday, Houston police released graphic body camera footage of the aftermath of the shooting of Alva Braziel, a black man apparently holding a gun who was killed soon after officers came across him in the street on 9 July.

Austin’s police department faced scrutiny and criticism after an unarmed and naked black teenager, David Joseph, was shot dead in February on a suburban street by a police officer responding to calls of a disturbance. The officer, Geoffrey Freeman, who is black, was fired but not indicted on criminal charges by a grand jury.

The new video’s depiction of the rapid escalation of what should have been a routine traffic stop into a physical confrontation after a white officer claims he has not received immediate compliance from a black woman recalls the arrest of Sandra Bland near Houston the following month.

Her case attracted national attention after she was found dead in her jail cell three days later, with the autopsy report stating she hanged herself with a plastic trash bag.

The state trooper who stopped her, Brian Encinia, was fired but avoided criminal prosecution for his conduct during the arrest, though later this year he is expected to stand trial on a perjury charge related to his stated reason for why he removed Bland from her car. He pleaded not guilty in March.

Bland’s mother, Geneva Reed-Veal, filed a civil wrongful death lawsuit last year. The trial in Houston federal court is set for January, but on Wednesday the case was referred to mediation in the hope of the parties reaching a settlement.