A female Tulsa police officer charged with manslaughter in the fatal shooting of an unarmed black man was released on bond early Friday.

Tulsa officer Betty Shelby "reacted unreasonably" when she fatally shot 40-year-old Terence Crutcher on Sept. 16, prosecutors wrote in an affidavit filed with the charge on Thursday.

She was booked on the charge after slipping into the Tulsa County jail at 1:11 a.m. Friday. She was in custody for 20 minutes and then released on a $50,000 bond, according to jail records.

The Oklahoma state medical examiner’s office said Friday that Crutcher died from a "penetrating gunshot wound of chest.”

Dashcam and aerial footage of 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.

But Crutcher's family immediately discounted that claim, saying the father of four posed no threat to the officers. And police said Crutcher did not have a gun on him or in his vehicle.

The affidavit filed Thursday indicates that Shelby "cleared the driver's side front" of Crutcher's vehicle before she began interacting with Crutcher, suggesting she may have known there was no gun on the driver's side of the vehicle.

The affidavit says Shelby told police homicide investigators that "she was in fear for her life and thought Mr. Crutcher was going to kill her. When she began following Mr. Crutcher to the vehicle with her duty weapon drawn, she was yelling for him to stop and get on his knees repeatedly."

Shelby’s quick arrest came after police acted quickly to provide videos of the shooting to black community leaders and members of Crutcher's family and then released them to the public.

The swift action in Tulsa, a city with a long history of tense race relations, stood in in contrast to Charlotte, North Carolina, where police refused under mounting pressure Thursday to publicly release video of the shooting of another black man this week and the National Guard was called in after two nights of violent protests. Demonstrations in Tulsa since Crutcher's death have been consistently peaceful.

Tulsa Mayor Dewey Bartlett praised the police department for quickly providing evidence to District Attorney Steve Kunzweiler's office.

"These are important steps to ensure that justice and accountability prevails," Bartlett said in a statement. "We will continue to be transparent to ensure that justice and accountability prevails."

Phil Turner, a Chicago-based defense attorney and former federal prosecutor, said the motivation of prosecutors in Tulsa may have been partly to allay outrage and avoid the kind of violence Charlotte has seen.

"But I don't think the charge was only to give the crowd some blood. ... No. I think (prosecutors) must have thought charges were warranted," he said.

If convicted, Shelby faces between four years and life in prison.

Crutcher's twin sister, Tiffany Crutcher, said her family is pleased with the charge, but she and her attorneys want to ensure a vigorous prosecution that leads to a conviction.

Attorney Damario Solomon-Simmons said: "We are happy that charges were brought, but let me clear — the family wants and deserves full justice.

"Not only for this family, not only for Terence but to be a deterrent for law officers all around this nation to know that you cannot kill unarmed citizens."

Shelby's attorney, Scott Wood, did not immediately respond to telephone messages seeking comment on the charges.

Meanwhile, a community college in Tulsa planned to hold a remembrance ceremony to honor Crutcher.

The ceremony was scheduled to be held at Tulsa Community College at noon Friday.

Crutcher was a student there. He had been scheduled to begin a music appreciation class at the college on Sept. 16, though the course was canceled a day earlier because of low enrollment.

The Associated Press contributed to this report.