Community activists say that Jamar Clark was unarmed and handcuffed when he was shot shortly after midnight on Sunday.
Officials confirmed Clark was unarmed and said they were still investigating whether he was handcuffed.
"There were handcuffs on the scene at the time. And we are still examining whether or not they were on Mr. Clark or whether they were just fallen at the scene," Minnesota Bureau of Criminal Apprehension Superintendent Drew Evans said at a news conference on Tuesday.
The deaths of unarmed black people at the hands of police in the United States over the past year have fueled protests nationwide and rekindled a national civil rights movement called Black Lives Matter.
Clark was taken off life support on Monday evening, his family told local media.
The Hennepin County Medical Examiner's Office said in a statement on Tuesday evening that Clark died of a gunshot wound to the head, and reported the time of death as Monday at 9:25 p.m. at the Hennepin County Medical Center. The office deemed Clark's death a homicide.
The Bureau of Criminal Apprehension, a unit of the Minnesota Department of Public Safety, will hand the results of its investigation to prosecutors in two to four months, Evans estimated.
A federal civil rights investigation is also taking place.
Activists blocked the entrance of a police precinct following the shooting and briefly flooded an Interstate highway late on Monday, demanding that authorities release video in the shooting.
At least 50 people were arrested after blocking a section of Interstate 94 that runs through Minneapolis.
Mayor Betsy Hodges said in a statement on Facebook that she did not have the authority to fulfill protester demands, such as firing the officers involved and releasing video, and asked for patience.
"I hear people's frustration. This process is going to require patience on all of our parts, including my own," she said.
Evans said there was no video of the shooting from police dashboard or body cameras. He said investigators are reviewing video from business and security cameras in the area, as well as from witnesses' cellphones, but none of those videos captured the entire incident.
The footage will not be released as it could taint witness interviews, Evans said.
In the incident, two Minneapolis police officers responded to a request for assistance from paramedics who reported that an individual disrupted their ability to help an assault victim.
The BCA said Clark was a suspect in the assault and that there was an altercation between him and the officers before one of them shot him.
The BCA said the officers' names will be released after they are interviewed by investigators. Both have been placed on administrative leave.
(Additional reporting and writing by Suzannah Gonzales and Fiona Ortiz in Chicago; Editing by Jonathan Oatis, Tom Brown and Ken Wills)
