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An Oklahoma police officer has been charged with manslaughter for the fatal shooting of an unarmed black man after the Tulsa County District Attorney’s Office found she “reacted unreasonably” and became “emotionally involved to the point that she overreacted.”

Officer Betty Shelby was charged with manslaughter in the first degree for the shooting of Terence Crutcher on Friday night, Tulsa County District Attorney Steve Kunzweiler said at a press conference Thursday afternoon.

“In the matter of the death of Terence Crutcher, I determine that the filing of the felony crime of manslaughter in the first degree against the Tulsa Police officer Betty Shelby is warranted,” Kunzweiler said.

Related: Tulsa Cop's Past Under Scrutiny After Terence Crutcher Shooting

Crutcher, 40, was shot and killed as he approached his SUV with his arms raised late Friday. The incident was caught on police helicopter and dashcam video.

The video footage, released on Monday, showed Crutcher slowly walking from the edge of a street north of Tulsa toward his vehicle, which authorities said had been reported abandoned and left running in the middle of the road at around 7:30 p.m. (8:30 p.m.ET).

An officer follows Crutcher from behind for several seconds with a gun drawn before three more officers then converge on the scene as Crutcher walks toward the SUV.

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As Crutcher is standing next to the driver’s side door, he suddenly drops to the ground and blood can be seen saturating his white shirt.

Tulsa Police Chief Chuck Jordan had said at a press conference on Monday that Shelby fired at Crutcher after telling a dispatcher that he was not cooperating. Another officer, Tyler Turnbough, tasered Crutcher before Shelby fired, Jordan said.

Officer Shelby had been assigned to a domestic violence call Friday evening when she came upon Crutcher and his vehicle in the road, according to an affidavit requesting a warrant for Shelby’s arrest.

Shelby approached the vehicle and asked Crutcher if it belonged to him and was disabled, but Crutcher was mumbling to himself and not answering her questions, according to the affidavit.

At that point, Crutcher walked toward his vehicle with his hands up and did not respond to Shelby’s commands for him to stop. Officer Turnbough then arrives and after Crutcher he reached in the driver’s side front window of his vehicle, he fired his Taser and Shelby fired one shot striking Crutcher in the lung, according to the affidavit.

Shelby’s lawyer, Scott Wood, has said that she believed Crutcher was under the influence of “some kind of narcotic, possibly PCP” and that Shelby is a certified “drug recognition expert.”

Crutcher's family lawyers have disputed that he reached inside his car, saying video evidence shows the car’s windows were up and blood seen on the windows corroborates that the windows were rolled all the way up at the time of the shooting.

Tulsa's police chief has said Crutcher was unarmed and that no weapon was found on him or in his SUV.

The chief investigator for the district attorney’s office said in an affidavit Shelby “reacted unreasonably by escalating the situation from a confrontation with Mr. Crutcher, who was not responding to verbal commands and was walking away from her with his hands held up, becoming emotionally involved to the point that she overreacted.”

Tiffany Crutcher, Terence's twin sister, said at a press conference later Thursday that her family was pleased to learn "the officer who senselessly killed my beloved twin brother" had been charged.

"We understand that nothing will bring him back," she said. "Our goal now as a family is to ensure that this never happens to another innocent citizen ... We lost a wonderful soul."

Family lawyer Damario Solomon-Simmons said at the press conference that even if Crutcher was not responding to Shelby's commands that did not warrant the deadly shooting.

"Failure to comply does not justify shooting someone," he said.

A warrant was issued for Shelby's arrest and early Friday morning she was booked into a Tulsa County jail and released on $50,000 bond, according to court documents.

Shelby, who was hired in 2011, had been placed on administrative leave with pay.

Governor Mary Fallin of Oklahoma said in a statement Thursday she hopes the decision "provides some peace to the Crutcher family and the people of Tulsa, but we must remain patient as the case works its way through the justice system, where a jury likely will be asked to decide whether officer Betty Shelby is guilty of the crime."

Related: The History of the Police Dashcam

"No matter how you feel about the prosecutors’ decision in this case, I hope Oklahomans will respect the views of your friends and neighbors because we still have to live peacefully together as we try to make sense of the circumstances that led to Mr. Crutcher’s death,” Fallin said in the statement.