A female Tulsa police officer was charged with first-degree manslaughter Thursday in the fatal shooting of an unarmed black man.

Tulsa County District Attorney Steve Kunzweiler filed the charge against Officer Betty Shelby after viewing dashcam video and helicopter video of the Sept. 16 shooting, according to a statement from his office.

The statement said Kunzweiler reviewed 911 calls, witness interviews and other information before making the decision to charge Shelby. Kunzweiler said arrangements were being made for Shelby's surrender.

"I do not know why things happen in this world the way they do," Kunzweiler said, adding that he determined first-degree manslaughter the appropriate charge. "We need to pray for wisdom and guidance."

Video from the shooting and its aftermath showed Crutcher walking away from Shelby with his arms in the air. The footage does not offer a clear view of when Shelby fired the single shot that killed Crutcher. Her attorney has said Crutcher was not following police commands and that Shelby opened fire when the man began to reach into his SUV window.

Crutcher's family immediately discounted that claim, saying the father of four posed no threat to the officers, while also pointing to an enlarged photo from police footage that appears to show Crutcher's window was rolled up.

Police have said Crutcher did not have gun on him or in his vehicle.

"The tragic circumstances surrounding the death of Mr. Crutcher are on the hearts and minds of many people in this community," Kunzweiler said. "It's important to note that despite the heightened tensions felt by all, which seemingly beg for an emotional response and reaction, our community has consistently demonstrated the willingness to respect the judicial process.

Among the definitions in Oklahoma for first-degree manslaughter is a killing "perpetrated unnecessarily either while resisting an attempt by the person killed to commit a crime, or after such attempt shall have failed."

"We are happy that charges were brought, but let me be clear, the family wants and deserves full justice," said Solomon Simmons, the family's attorney.

"Never lose sight of these cases," he added. "It's not about hashtags, it's about people."

If convicted, Shelby could face a minimum of four years in prison.

Shelby, who joined the Tulsa Police Department in December 2011, was on her way to a domestic violence call when she encountered Crutcher's vehicle abandoned on a city street, straddling the center line.

Shelby did not activate her patrol car's dashboard camera, officials said, so no footage exists of what first happened between the two before other officers arrived.

The police footage shows Crutcher approaching the driver's side of the SUV, then more officers walk up and Crutcher appears to lower his hands and place them on the vehicle. A man inside a police helicopter overhead says: "That looks like a bad dude, too. Probably on something."

The officers surround Crutcher and he suddenly drops to the ground. A voice heard on police radio says: "Shots fired!" The officers back away and Crutcher is left unattended on the street for about two minutes before an officer puts on medical gloves and begins to attend to him.

Tulsa Mayor Dewey Bartlett said police worked quickly to provide Kunzweiler with the information he needed to decide whether to charge the officer.

"I appreciate their efforts as well as the District Attorney's usual thorough evaluation of the rules of law for which we are all accountable," Bartlett said in a written statement. "These are important steps to ensure that justice and accountability prevails.

"We will continue to be transparent and ensure the system carries out its responsibility to provide justice."

Earlier this year, a former volunteer deputy with the Tulsa County Sheriff's Office was sentenced to four years in prison after he was convicted of second-degree manslaughter in the shooting death of Eric Harris.

The Associated Press contributed to this report.