The death of a black man at the hands of the police during an incident in Minneapolis has generated protests in that city in the United States.
Jamar Clark, 24, was in intensive care in hospital after being shot in the head last Sunday.
Police say he was a suspect in a case of assault and had interfered with doctors attending to a victim when he was shot.
But some claim that he was handcuffed when he was shot.
The protests have been brought against the police station, where protesters are camped for two days, and have also blocked a main road.
On Monday night, 51 protesters were arrested.
"Handcuffed"
Police released details of the shooting against Clark and denied reports that claim that he had already been handcuffed when the shooting occurred.
The demonstration began after the mayor of the city asked the federal government to launch an investigation into violations of civil rights.
One of the main highways of the city was closed by the protests.
Although a state agency has already launched its own criminal investigation, Mayor Betsy Hodges said the city needs "all the tools at our disposal."
The two officers involved have been given paid leave, a customary procedure in such cases.
According to police, the incident began Sunday, when authorities were called north of Minneapolis, after an assault it is reported.
At the scene, police found Clark interfering with the paramedics who tried to assist the victim.
Protesters say they will camped outside the police station until the facts are clarified.
They tried to calm him, which resulted in a scuffle and shot, according to police.
Clark's father told the AP that his son was shot over the left eye.
The brother confirmed to the same agency that the family had gathered at the hospital on Monday, to disconnect the apparatus that kept him alive.
Video
The police chief said that officers were not carrying cameras on their uniforms, but said if there was video patrol car or some other means of surveillance had captured the incident.
The demonstrators welcomed the federal investigation but said they would continue their protest until any video of the situation is reported and the police officers involved are identified.
"We will not move until we get those images," said Michael McDowell, a member of the movement "Black Lives Matter" ("The lives of black matter").
In the United States there have been a number of high-profile incidents in which police have fired on black guys.
That has generated protests across the country against the use of excessive force by the authorities against the African American community.