The US police officer who fatally shot Justine Damond has been charged with her murder.

The Minneapolis police officer who shot and killed Australian woman Justine Damond last July has turned himself into law enforcement and is now facing murder and manslaughter charges.

According to local news site Star Tribune, Officer Mohamed Noor, who originally refused to speak to investigators about the incident, turned himself into Hennepin County Jail after a warrant was issued for his arrest.

Jail records show he has been charged with third-degree murder for “perpetrating an eminently dangerous act and evincing depraved mind” and second-degree manslaughter for “culpable negligence creating unreasonable risk”. His bail has been set at US$500,000 (AU$650,000), according to records.

Officer Noor has been on fully-paid “administrative leave” since the shooting.

In a joint statement released by 40-year-old Justine’s fiancé, Don Damond, and her father John Ruszczyk, her family called called Officer Noor’s arrest “one step toward justice for this iniquitous act”.

“We waited over eight months to come to this point,” the statement read, thanking law enforcement officials for their “diligent” and “thorough” investigation.

"We remain hopeful that a strong case will be presented by the prosecutor, backed by verified and detailed forensic evidence, and that this will lead to a conviction.

"No charges can bring our Justine back. However, justice demands accountability for those responsible for recklessly killing the fellow citizens they are sworn to protect, and today's actions reflect that."

If convicted of third-degree murder, Noor could face a maximum of 25 years in prison, though the presumptive sentence is half of that, Star Tribune reports.

The second-degree manslaughter charge carries a maximum sentence of 10 years in prison, but the presumptive sentence is four years.

Justine was killed on July 15 outside her home in south Minneapolis home, after she called police to the area fearing a sexual assault was taking place near her house.

Minneapolis police officer Mohamed Noor turns himself in on charges in Justine Damond killing https://t.co/qYsndYj29i pic.twitter.com/9u9NV8jFkf

— Star Tribune (@StarTribune) March 20, 2018

In 911 transcripts released shortly after her death, Justine can be heard telling emergency operators she wasn't sure if a woman outside her house was "having sex or being raped".

"I think she just yelled out 'help' but it's difficult," she said.

"The sound has been going on for a while, but I think, I don't think she’s enjoying it."

Eight minutes later, at 11.35 pm, Damond called 911 again to ensure police were still coming to the scene. She confirmed her address and told the operator the woman in question was still screaming.

Minutes later, Justine, who was due to marry her fiancé just a month after her death, was shot and killed by one of the responding officers. It's believed 31-year-old Officer Mohamed Noor shot across his partner, Officer Matthew Harrity, 26, through the open driver's side window, hitting Damond in the abdomen.

Both officers performed CPR on Justine for four minutes until paramedics arrived, but she could not be saved and was declared dead at the scene.

Matthew Harrity later told investigators he had been startled by a loud noise right before Justine approached the driver's side window of their police car. It was then that Noor fired his weapon from the passenger seat.

The officers did not turn on their body cameras until after the shooting, and there was no squad camera video of the incident.

Days after her death, Officer Noor offered condolences to her family, via a statement from his attorney.

"Officer Noor extends his condolences to the family and anyone else who was been touched by this event," the statement read.

"He takes their loss seriously and keeps them in his daily thoughts and prayers."

A press conference will be held later today to provide more information about the charges against Officer Noor.

Amelia Lester explains why the aftermath of the school shooting in Florida feels different to that of any shooting before it.