Police dashcam video shows a Texas state trooper tried to pull Sandra Bland out of her car, then drew his stun gun and threatened her after the woman who authorities say later killed herself in a jail cell refused to follow his orders.

The roadside encounter swiftly escalated into a shouting confrontation, the video released Tuesday shows, as the officer attempted to drag 28-year-old Sandra Bland from her vehicle, with the officer at one point saying, "I will light you up," as he held the stun gun.

Days later, Bland was found dead in the jail cell in a case that has caused her family and supporters to dispute that she hanged herself with a plastic garbage bag, as authorities have said.

The video posted online by the Texas Department of Public Safety shows the trooper stopping Bland for failure to signal a lane change. After he hands her a written warning, the trooper remarks that Bland seems irritated. The Illinois woman replies that she is irritated because she had changed lanes to make way for the trooper's car.

The conversation quickly turns hostile when the officer asks Bland to put out her cigarette and she asks why she can't smoke in her own car. The trooper then orders Bland to get out of the vehicle. She refuses, and he tells her she is under arrest.

Further refusals to get out bring a threat from the trooper to drag her out. He then pulls out a stun gun and makes the threat about lighting Bland up.

When she finally steps out of the vehicle, the trooper orders her to the side of the road. There, the confrontation continues off-camera, but it is still audible. The two keep yelling at each other as the officer tries to put Bland in handcuffs and waits for other troopers to arrive.

Out of the camera's view, Bland goes on protesting her arrest, repeatedly using expletives and calling the officer a "pussy." She screams that he's about to break her wrists and complains that he knocked her head into the ground.

Her death comes after nearly a year of heightened national scrutiny of police and their dealings with black suspects, especially those who have been killed by officers.

The case has resonated on social media, with posts questioning the official account and featuring the hashtags #JusticeForSandy and #WhatHappenedToSandyBland. Others referred to #SandySpeaks, the hashtag Bland used in monologues she posted on Facebook in which she talked about police brutality and said she had a calling from God to speak out against racism and injustice.

In an affidavit released Tuesday, the trooper said that after handcuffing her for becoming combative, she swung her elbows at him and kicked him in his right shin.

Trooper Brian Encinia said he then used force "to subdue Bland to the ground," and she continued to fight back. He arrested her for assault on a public servant.

The trooper, who has been on the force for just over a year, has been placed on administrative leave for violating unspecified police procedures and the Department of Public Safety's courtesy policy. The agency would not address questions about whether the trooper acted appropriately by drawing his stun gun or pulling her out of the vehicle.

"Regardless of the situation — it doesn't matter where it happens — a DPS state trooper has got an obligation to exhibit professionalism and be courteous ... and that wasn't the case in this situation," said Steven McCraw, the department director.

A law enforcement expert from Maryland said he was troubled by the video "from start to finish."

Vernon Herron, a senior policy analyst with the University of Maryland Center for Health and Homeland Security, said if the trooper intended to give her a warning, that's what he should have done, no matter what the woman said to him.

"A person's attitude or their demeanor is not probable cause to make an arrest," said Herron, who has more than 35 years of experience in public safety and law enforcement.

Court records show Bland had several encounters with police in both Illinois and Texas over the past decade, including repeated traffic stops and two arrests for drunk driving, one of which was later dismissed.

Bland was taken to the Waller County Jail about 60 miles northwest of Houston on July 10 and found dead July 13. A Texas Rangers investigation into her death is being supervised by the FBI.

Although a medical examiner has ruled Bland's death a suicide, supporters insist she was upbeat and looking forward to a new job at Prairie View A&M University, where she graduated in 2009. Bland's family and clergy members have called for a Justice Department probe, and an independent autopsy has been ordered.

At a memorial service Tuesday night at Bland's alma mater, her mother, Geneva Reed-Veal, reiterated that she doesn't believe Bland took her own life. She also spoke of her grief, saying, "I have a baby to put in the ground."

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Associated Press writer Jamie Stengle contributed to this report from Dallas.

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Dashcam video posted by Texas Department of Public Safety: http://youtu.be/yf8GR3OO9mU .