A makeshift memorial is seen at the location where Jamar Clark was allegedly shot by police early Sunday, in Minneapolis, Minnesota, November 16, 2015. REUTERS/Todd Melby

(Reuters) – Minneapolis Mayor Betsy Hodges said on Monday she had requested a federal civil rights investigation into a police shooting over the weekend that seriously wounded a 24-year-old black man and set off protests.

Activists, who said Jamar Clark was unarmed and handcuffed when he was shot in the head on Sunday, blocked the entrance of a police precinct following the shooting and briefly flooded an interstate late on Monday, demanding that authorities release video of the incident. Police said he was not handcuffed.

“I have asked for this because we need all the tools we have available to us… a healthy investigative process is best for everyone, the family, the officers and the community,” Hodges said.

At least 50 people were arrested after blocking a section of the northbound Interstate 94 through Minneapolis during a protest over Clark’s shooting, police said. Demonstrators held signs including “Handcuffs, Don’t Shoot,” KMSP-TV reported.

The Minnesota Bureau of Criminal Apprehension was continuing its own investigation and will hand over the results to prosecutors.

Clark was shot in the head and was “brain dead” according to family members cited in local media. Reuters was not able to independently confirm Clark’s condition and officials said only that it was “unchanged.”

Minneapolis Police Chief Janee Harteau, who spoke at a news conference with Mayor Hodges, said that the names of two police officers involved would not be released yet.

Deaths of unarmed black men and women at the hands of police over the past year have fueled criticism over the treatment of minorities by police in the United States and rekindled a national civil rights movement under the banner Black Lives Matter.

Police said that at about 12:45 a.m. on Sunday, they responded to a report of an assault and shot a man during a struggle after he confronted paramedics and disrupted their ability to give aid.

The suspect was not in handcuffs during the physical altercation and was taken by ambulance to Hennepin County Medical Center, police said.

Witnesses said Clark was handcuffed when he was shot in the head and his body was removed quickly from the scene, according to a Black Lives Matter Minneapolis statement.

The Minneapolis National Association for the Advancement of Colored People said Clark “was murdered, execution style” by police.

Up to 20 witnesses said he was dead at the scene and his body was “lifeless,” Minneapolis NAACP spokeswoman Raeisha Williams said.