Texas authorities have released dash-cam footage showing a white police officer, during a routine traffic stop, argue with and arrest an unarmed black woman who later died in jail.
The death of 28-year-old Sandra Bland is being investigated as possibly suspicious, after authorities initially called her death on July 13 in Waller County jail an apparent suicide.
Bland's family have challenged the suicide diagnosis and Waller County District Attorney Elton Mathis on Monday said he was opening a murder investigation.
Bland was found dead in her cell on July 13, where police Captain Brian Cantrell said she had hanged herself with a plastic garbage bag.
Her family insisted she had travelled to Texas to start a new job at Prairie View A&M University, where she graduated in 2009. She was upbeat and anything but suicidal, they said.
Bland's death puts the spotlight anew on US police behaviour and brutality against black suspects.
A major complaint is how police often stop black drivers for minor traffic violations that end in injury and death.
In the recording from July 10 taken from the camera mounted on the dashboard of the police car in Hempstead, Texas, Bland is pulled over for failing to signal she was changing lanes.
Texas Ranger Brian Encinia takes Bland's driver's licence back to his cruiser, walks back to her car, leans into her window, and says: "OK, Mam, are you OK?"
"This is your job," Bland says.
"You seem irritated," Encinia says.
"I am a little irritated, but that doesn't stop you from giving me a ticket," Bland says.
But when Encinia asks Bland to "please" put out her cigarette, she objects.
"I'm in my car. Why do I have to put out my cigarette?" she asks, indignant.
"Well, you can step out now," Encinia demands. She objects, and Encinia repeatedly demands she step out or he will yank her out.
"Don't touch me. I'm not under arrest," Bland says.
"Get out of the car," Encina shouts repeatedly. "I will light you up."
The altercation escalates with curse words from Bland and shouts from Encinia. Finally, Encinia pulls Bland out of the car and knocks her while she is on the ground, according to a video taken by a bystander who is chased away by police.
"For a failure to signal! You feeling good about yourself, don't you...."
Bland complains that her wrists are being broken, and that Encinia has his knee in her back.
"This makes you feel real good, officer Encinia, for a traffic signal, knock me on the ground," she says.
Many of those who saw the footage were incensed, including Texas state senator Royce West, who declared that Bland did not deserve to be taken into custody.
"After you see that video, I think you will agree with me that Sandra Bland did not deserve to be arrested," he said after meeting Bland's family.
Lieutenant Governor Dan Patrick, who also met with Bland's kin, spoke of a "tragedy".
"She lost her life in the jail, and that's what we have to look at," he said.
West said he concluded she had been threatened with a Taser after he reviewed the video, The Washington Post reported.
Three days after the arrest, Bland was found dead in her jail cell.
District Attorney Mathis said that Bland's family had made a "valid point" that she had a lot of things going on in her life that were good.
"It's very much too early to make any kind of determination that this was a suicide or a murder because the investigations are not complete," he said.
Encinia has been put on desk duty pending a full investigation, the Texas Department of Public Safety said. The department has also asked that the FBI assist in the investigation.
