According to the Chicagotribune, Oakland became a focal point of protests against economic inequality that swept the United States last October.
Police removed dozens of campers from a plaza in front of Oakland City Hall on October 25. Later that day, they fired tear gas and flash bang grenades at hundreds of protesters who had gathered at the plaza.
The military veteran, Scott Olsen, was struck in the head and became a national symbol of the protest movement.
One police officer fired tear gas into a crowd that was trying to help Olsen, yet a criminal investigation into these events was closed, the consultant's report said.
"It is our belief that OPD should consider a re-examination of the quality of this investigation," the report said.
It said poor staffing, outdated crowd control policies and lack of coordination contributed to the overall handling of Occupy.
"Aircraft accident investigations frequently reveal that airplane crashes are caused by a series of cascading events, not a singular problem," the report said, adding that "this analogy appropriately describes our observations within the Oakland Police Department."
City officials on Thursday said the department had already implemented several reforms.
"This is not an easy report to release, but we are committed to confronting the truth," Mayor Jean Quan said in a statement.
A representative for the Occupy protesters could not immediately be reached.
While the report noted many problems with the department, it complimented newly installed Police Chief Howard Jordan for making improvement his highest priority.
Oakland police officials announced in April that the department was making significant changes to how it trains officers to control large crowds following criticism of its handling of the Occupy protests. It received more than 1,000 misconduct complaints during those protests.