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Investigators are working to determine whether Jamar Clark, a 24-year-old unarmed black man shot by Minneapolis police, was handcuffed during the incident that subsequently sparked mass protests and led to dozens of arrests across the city.

Police initially denied that Clark was restrained when an officer shot him in the head shortly after midnight Sunday. But investigators later found handcuffs at the scene.

"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 Tuesday.

The county medical examiner's office announced Clark's death Monday after his family removed him from life support, a day after the shooting. The office deemed Clark's death a homicide.

Police said the incident began when they were called to North Minneapolis around 12:45am Sunday following a report of a domestic assault. When they arrived, police said, they saw a man (later identified as Clark) interfering with paramedics who were helping the victim. Officers tried to calm him, but there was a struggle and an officer fired at least once, Evans said, hitting the man.

Evans said investigators are reviewing video footage from business and security cameras in the area, as well as from witnesses' cellphones, but noted that none of the videos captured the entire incident. The footage will not be released out of concern that it could taint witness interviews, he added. There was no video of the shooting from police dashboard or body cameras.

The death is the latest in a string of high-profile shootings that have sparked protests against excessive and fatal use of police force across America. Shortly after the Minneapolis shooting, activists blocked the entrance of a police precinct and briefly flooded an Interstate highway late on Monday, demanding that authorities release video of 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.

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.