Portland Mayor Tom Potter and Police Chief Rosie Sizer promise a speedy investigation into the death of 42-year-old James Chasse while in police custody last week.
Chasse died as Portland police officers were attempting to arrest him in northwest Portland.
Police said Chasse was not cooperating with authorities and his behavior was bizarre.
Witnesses said police placed a Taser gun to his torso and kicked him in the chest and neck. They also said Chasse resisted arrest by biting police officers.
The state medical examiner determined that Chasse died from broad-based trauma to the chest. The examiner also ruled the death as accidental.
Chasse’s family admits that he had mental health problems but said police have been uncooperative in explaining their actions.
"This event has made my family and many others truly question how great a city this really is. You cannot treat any person in Portland like yesterday’s trash and expect to be considered a model for anything," said Mark Chasse, Chasse’s brother, at a news conference.
Sizer said she expects investigators to release a timeline and statements from officers and witnesses.
Sizer said she expects the Multnomah County district attorney to send the investigation to a grand jury.