Milwaukee County District Attorney John Chisholm has concluded that former officer Christopher Manney acted in self-defense.
"Manney's use of force in this incident was justified self-defense and that defense cannot be reasonably overcome to establish a basis to charge (former) officer Manney with a crime," Chisholm says.
Dontre Hamilton's family released a follow-up to the DA report.
"After waiting now for almost eight months since Dontre Hamilton was shot and killed at Red Arrow Park by former City of Milwaukee Police Officer Christopher Manney, the Hamilton family and their attorneys are extremely disappointed in District Attorney John Chisholm’s decision in this case," Dontre Hamilton's family's statement says. "This is a case which cries out for justice, criminal charges against Christopher Manney, and accountability to Dontre Hamilton’s family."
Former officer Manney said he moved to frisk Hamilton in Red Arrow Park and Hamilton resisted, striking the officer with his own baton. Manney then opened fire 14 times, killing Hamilton.
The 31-year-old was mentally ill and unarmed.
Two other officers responded earlier to calls of concern about Hamilton, but concluded he was not a threat.
MPD Chief Edward Flynn later fired Manney for failing to follow protocol that led to the fatal shooting.
Some Hamilton family members had expressed the wish that the DA not announce his decision, in the days leading up to Christmas.
Late Friday, following what has become regular demonstrations at Red Arrow Park by family supporters, some demonstrators walked onto I-43 during afternoon rush hour and blocked traffic.
Police arrested 74 people who refused to leave the freeway, charging them with a range of offenses.
Several U.S. cities have been the scenes of protests in recent times, over white police officers killing black men.
Update: The U.S. Justice Department announced it will review the case to determine if Dontre Hamilton's civil rights were violated.