More than 30 police officers have been subpoenaed as part of a grand jury investigation into the fatal police shooting of an Australian woman in Minneapolis.

The grand jury is scheduled to begin its work Tuesday as prosecutors decide whether to charge Officer Mohamed Noor in the July death of 40-year-old Justine Ruszczyk Damond. She was shot in an alley as Noor and his partner responded to her call about a possible sex assault behind her home.

Minneapolis’ police union president, Bob Kroll, says most of the 30 officers subpoenaed to testify are Noor’s trainers and academy educators.

Hennepin County Attorney Mike Freeman convened the grand jury as he weighs whether to charge Noor, who has refused to speak with investigators. Noor’s partner told investigators that Noor fired his weapon after hearing a loud noise right before Damond approached their police SUV.