At least half a dozen police officers have appeared before a grand jury in Minneapolis in the fatal police shooting death of Australian woman Justine Damond.
It is part of an ongoing effort by prosecutors to determine whether there is enough evidence to charge Officer Mohamed Noor, who shot and killed Ms Damond Ruszczyk in July last year.
Ms Damond Ruszczyk was shot and killed in the alley behind her Minneapolis home after she made a 911 call to report a possible sexual assault.
More than 30 police officers in Minneapolis have been subpoenaed to testify before the grand jury in the case.
"To say officers and their families were unhappy is an understatement," Police Officers Federation president Bob Kroll told the ABC.
The police union was initially unwilling to defend Mr Noor after the shooting but was unhappy dozens of officers had been subpoenaed for the grand jury hearings.
He described the manner in which officers were served (just days after the city hosted the Super Bowl — a large police operation where many local cops racked up hours of overtime) as "disrespectful" and "distasteful".
It was understood some of those officers would appear before the grand jury today.
Because of the secretive nature of grand jury proceedings it was unclear what the officers would be asked.
The Police Officers Federation of Minneapolis briefed those who had been subpoenaed yesterday and said there was a lot of "confusion" and "nervousness" among the officers who had been served.
The subpoenaed officers include former trainers, field training officers and supervisors of Officer Noor and his partner Matthew Harrity, who was at the scene when Ms Damond Ruszczyk was killed.
Some of those subpoenaed may have had nothing to do with either officer for years.
"It's unprecedented," Mr Kroll said.
"I've never seen anything like it," he said.
Mr Kroll has been president of the federation since 2015.
Ms Damond Ruszczyk's family in Australia previously criticised the investigation into their daughter's death, as had Hennepin County Attorney Mike Freeman.
Family friends have also asked the officer who killed her to have a heart and speak to investigators.
Mr Freeman previously said he would no longer use grand juries in police shooting cases, but his office confirmed that grand jury was underway.
Mr Freeman was previously covertly recorded telling activists the poor initial investigation meant he had to gather extra information.
Officer Noor has never spoken publicly about the case and has declined to speak to investigators.
Mr Freeman said he would still make the final decision on whether to file charges.