A white police officer has been charged with first-degree manslaughter after she shot an unarmed black pastor dead while he had his hands up.

Prosecutors in Tulsa, Oklahoma, have filed charges against Betty Shelby after she fatally gunned down 40-year-old Terence Crutcher on September 16.

Dashcam and aerial footage of the shooting and its aftermath showed Crutcher walking away from Shelby with his arms in the air.

A warrant has been issued for her arrest and arrangements are now being made for her to surrender. If convicted, she faces between fours years and the maximum sentence of life in prison.

The Tulsa County District Attorney's office said Officer Shelby 'reacted unreasonably by escalating the situation' by 'becoming emotionally involved to the point that she overreacted.'

Crutcher's twin sister, Tiffany, spoke to reporters outside of the Tulsa County Courthouse on Thursday and said that the family is pleased Shelby has been charged.

Betty Shelby (left) has been charged with first-degree manslaughter after shooting unarmed black man Terence Crutcher (right) dead

Crutcher, 40, pictured with his twin sister, Tiffany, was shot dead while his arms were in the air

She said that they hope the district attorney vigorously prosecutes the case and obtains a conviction.

Tiffany added that she hopes a criminal conviction will help bring an end to the killing of innocent citizens by police.

Oklahoma Gov. Mary Fallin said she hopes a first-degree manslaughter charge against Shelby provides some peace to the man's family and to the people of Tulsa.

In a statement Thursday, Fallin complimented Tulsa's police chief, mayor, district attorney and citizens for helping to keep peace and order "during this difficult time."

Fallin also urged Tulsa residents to be patient as the case works its way through the justice system and noted that Shelby is innocent until proven guilty.

Crutcher's death sparked huge protests, with demonstrators demanding Shelby's arrest.

Video shows Crutcher (pictured in a white t-shirt) had his hands up when he was gunned down by police officers on September 16

The footage of the moments before and after the shooting 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 gun on him or in his vehicle.

Shelby, who joined the Tulsa Police Department in December 2011, was en route 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, so no footage exists of what first happened between the two before other officers arrived.

A close-up from a dashcam shows the moments before Crutcher was shot. His death caused an outcry in Tulsa

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.

AUDIO FROM HELICOPTER OFFICER 1: 'He's got his hands up for her now. 'This guy's still walking and not following commands.' OFFICER 2: 'Time for taser I think.' OFFICER 1: 'I've got a feeling this is going to happen.' 'That looks like a bad dude too, Probably on something.' VOICE OVER THE RADIO: 'I think he may have been tasered. 'We've got shots fired... suspect down.' Advertisement

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.

Police also said they found a vial of PCP in Crutcher's vehicle after the deadly shooting.

They have refused to say whether pastor Terence Crutcher was high at the time of his death until the results of an autopsy.

PCP or phencyclidine, also called angel dust, can cause slurred speech, loss of coordination and a sense of strength or invulnerability.

At high doses, it can cause hallucinations and paranoia.

Scott Wood, Shelby's attorney, gave her version of events to ABC News just before the charges were filed.

Aerial footage shows the moments before he was fatally shot by Shelby

He said: 'She is very distraught about the incident.

'The fact that she has taken a human life but at the same time she wants the Cructher family to know she meant no ill will.

'This wasn't done out of hate or anger. She stopped there that day to help somebody.

'Things didn't go the way they should have. And it ended up as an officer-involved shooting.

'She was on her way to a domestic disturbance call.'

As she was driving she came across Crutcher, who according to Shelby was in the middle of the road looking down.

His SUV was blocking traffic. The engine was still running, which Shelby thought was odd, as she assumed it had broken down.

Wood said it is 'important to remember' that Shelby was on the scene for around a minute-and-a-half before the shots were fired.

Crutcher, pictured in the white shirt being filmed by a Tulsa Police helicopter after his car broke down in the middle of the road on Friday night, was shot dead shortly afterwards

Officers followed Crutcher back to his car with their weapons drawn

Officers in the helicopter predicted their ground colleagues were going to use their taser

Seconds later, Crutcher was laying on the ground with the call 'shots fired' on the radio

When Shelby asked Crutcher, pictured left with his father, if he was the owner of the stalled SUV, he allegedly mumbled incoherently in response

When Shelby approached the car, the doors were closed, and the windows were open. She then saw Crutcher walking toward her, Wood said.

The lawyer then said Shelby asked Crutcher: 'Hey, is this your car?'

Crutcher didn't respond, simply dropping his head while continuing to look at Shelby, 'kind of under his brow,' Wood told ABC.

Crutcher then began to put his hand into his left pocket, so Shelby told said: 'Hey, please keep your hands out of your pocket while you're talking to me. Let's deal with his car.'

He then pulled his hand away and put his hands up in the air, even though he was not instructed to do so.

Wood said that his client also found this odd.

People hold signs at a 'protest for justice'. Around 100 people gathered at the scene of the shooting earlier this week

When Shelby tried to talk to Crutcher, he just mumbled in response, Wood claims.

By around this point, Shelby, a drug recognition expert, believed Crutcher was 'on something,' Wood said.

Shelby radioed in that she had a subject 'who is not following commands.' She out her gun and told Crutcher to get on his knees, Wood said.

She pulled out a gun instead of a Taser because she thought he had a weapon.

Her initial plan was to book him for public intoxication, Wood told ABC.

Shelby ordered Crutcher to stop multiple times as Crutcher walked toward the SUV with his hands up, Wood said.

But those orders cannot be heard on the dashcam video.

The clip which shows the fatal shooting starts as another patrol car pulls up to the scene. By this point, Shelby is already pointing the gun at Crutcher.

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.

Community leaders who watched the video expressed shock and outrage about what they saw, but called for a calm reaction