HEMPSTEAD, July 22

Authorities have released dashcam video of a white Texas police officer stopping a black motorist later found dead in a jail cell in what has become the latest case to cast national attention on the interactions between police and minorities in the United States.

Authorities say Sandra Bland, 28, hanged herself in her cell three days after her arrest, a contention her family and supporters dispute. The video doesn’t reveal what happened while she was in custody, but it depicts a heated confrontation after a minor traffic infraction in which the state trooper tried to drag Bland from her car, drew his stun gun and threatened that he would “light you up.”

The video posted by the Texas Department of Public Safety on Tuesday 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 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 what appears to be a weapon and says, “I will light you up.”

The dashboard video shows that when Bland finally steps out of the vehicle, the trooper orders her to the side of the road. There, the confrontation continues off-camera but 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 continues protesting her arrest, repeatedly using expletives and calling the officer a “pussy.” At one point, she screams that he’s about to break her wrists and complains that he knocked her head into the ground. In the affidavit released yesterday, 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. He also said Bland swung her elbows at him and kicked him in his right shin.

The trooper has been placed on administrative leave for violating unspecified police procedures and the Department of Public Safety’s courtesy policy.