Christian Glass, 22, was shot five times after calling 911 for help during an apparent mental health crisis when his car got stuck on the side of a road near Denver.
His parents Sally and Simon Glass last month made an emotional plea for police be charged, accusing the officer who pulled the trigger of murder.
On Thursday, 5th Judicial District Attorney Heidi McCollum said she would present the case to a grand jury for further investigation and possible charges.
"After a comprehensive investigation, I now intend to bring this matter to the grand jury which, at my request, is scheduled to convene multiple times during the month of November," McCollum said in a statement.
"When a peace officer shoots and wounds or kills another in Colorado, there are specific protocols to investigate and review such matters. It is imperative that we reach the right decision and not rush into judgement - in fairness to the family of the victim, and those involved with and impacted by Christian's death.
"Most of all, I am absolutely committed to seeking justice in this case. The grand jury, through their subpoena power and sworn testimony, will aid us in reaching the right outcome. Once it is completed, I will share the findings with our community.
"The death of Christian Glass was a tragic event, and the condolences of my office remain with Mr Glass's family and friends through this difficult time."
A grand jury is a group of US citizens who determine if there is enough evidence to warrant charges in criminal cases.
In a statement released through their lawyers, Christian's parents Sally and Simon Glass vowed to pursue justice for their son.
"The wheels of justice are turning in the right direction, and we support the efforts and diligence of the 5th Judicial District Attorney, Heidi McCollum, to empanel a grand jury," they said.
"There is not an hour that passes that we do not think about our gentle son Christian Glass. We are expecting accountability for those involved in his murder."
In lengthy 911 audio Glass can earlier be heard saying he was stuck in a trap and feared he was going to be killed, prompting the dispatcher to tell police he sounded paranoid.
At the time, the Clear Creek County Sheriff's Office said Glass was argumentative and uncooperative and armed with a knife.
The Glass family disputed that version of events, insisting Christian had done nothing wrong and was simply too scared to get out of the car.
The sheriff's office had passed the case on to the Colorado Bureau of Investigation and announced plans to develop a ''crisis response team" for the area.
Christian Glass was born in Christchurch but his family moved to the US when he was 10.
