In an extraordinary letter published in the Minneapolis Star Tribune, Lieutenant Bob Kroll also questioned the objectivity and “lack of professionalism” of the top prosecutor, Hennepin County Attorney Mike Freeman, who will decide if Officer Noor will be charged.

Mr Freeman’s comments at a recent Minneapolis town hall meeting where he was quizzed by concerned residents about the July 15 shooting made headlines in the US and Australia and raised the ire of the police union head.

“Freeman’s comments that ‘I’m saddened by the death of this fine young woman’ and that ‘it didn’t have to happen — it shouldn’t have happened’ show he is focusing on the status of the person lost rather than the events leading to a tragic loss,” Lt Kroll, president of the Police Officers Federation of Minneapolis, who has previously declined to comment on the shooting, wrote. “This comment breaks with the imperative that fairness cross all socio-economic boundaries.

“We want an assurance that Noor will not be charged simply on the basis of Damond’s status as a fine young woman in a nice neighbourhood.

“The status of the deceased as a fine young woman, while true, is not and should not be part of an objective decision to charge anyone with a crime.

“This case is tragic, and so are the too many other deaths that have occurred in our city.

“This comment brings Freeman’s objectivity into question.”

Mr Kroll had previously told News Corp that he and other had received death threats over the case.

“Some have been very specific and others have been quite general death threats, not just to our office but to the 5th precinct (where Noor worked) and elsewhere,” he said. “In total there have been dozens of death threats They really aren’t helping anyone.”

Officer Noor, following legal advice, has declined to speak publicly or to investigators about the shooting.

Ms Damond’s death has added to already bubbling racial and police shooting turmoil in the US city.

An independent body has handed the results of its investigation to Mr Freeman, who has indicated he will decide by the end of the year if Somali-born Officer Noor will be charged.

Ms Damond’s family has also been vocal in calling for a transparent investigation where there “is no stone left unturned”.

“We trust that the Hennepin County Attorney’s determination will be based on an astute assessment of the facts,” the family wrote in a statement this week.

Ms Damond was shot by Officer Noor after she called 911 just before midnight on July 15 to report a woman screaming in her affluent Minneapolis neighbourhood.

When Ms Damond approached Officer Noor’s police car in an alley behind her Minneapolis home he shot across his partner and out the window of the car where the Australian was standing in her pyjamas.

Lt Kroll also argued in his letter “irresponsible comments by public officials are fuelling the creation of police widows and widowers”.