BALTIMORE — The Justice Department said Tuesday it has opened a civil rights investigation into the death of Freddie Gray, a black man who suffered a fatal spinal-cord injury under mysterious circumstances after he was handcuffed and put in the back of a police van.

After the probe was announced, at least 1,000 people gathered at a previously planned rally at the site of Gray’s arrest. Protesters marched to a police station a couple of blocks away, chanting and holding signs that read “Black Lives Matter” and “No Justice, No Peace” — slogans that have come to embody what demonstrators believe is widespread mistreatment of blacks by police.

Pricilla Jackson carried a sign reading, “Convict Freddie’s killers,” that listed the names of the six officers suspended with pay while local authorities and the U.S. Justice Department investigate the death. Jackson, who is black, said she wants Mayor Stephanie Rawlings-Blake to know that she and others have been brutalized by police.

“They’re hurting us when they throw us to the ground and kick us and punch us,” said Jackson, 53.

At least one an activist was detained when he jumped past police barriers.

Gray’s mother, Gloria Darden, was overcome with grief and carried away at one point by several men, writhing and sobbing uncontrollably, her face obscured by a hood and dark glasses. The crowd parted to let her through. Another female family member collapsed in tears and was helped away.

Gray, 25, was taken into custody April 12 after police “made eye contact” with him and another man in an area known for drug activity, police said. Gray was handcuffed and put in a transport van.

At some point during his roughly 30-minute ride, the van was stopped and Gray’s legs were shackled when an officer felt he was becoming “irate,” police said.

Police Commissioner Anthony Batts said Gray asked for an inhaler and several times asked for medical care. He eventually was rushed to a hospital.

Gray died Sunday — a week after his arrest — of what police described as “a significant spinal injury.”

Exactly how he was injured and what happened in the van is still not known.

Justice Department spokeswoman Dena Iverson said investigators are “gathering information to determine whether any prosecutable civil rights violation occurred.”

There’s a high threshold for bringing federal civil rights charges against police officers in such cases. Federal investigators must show an officer willfully deprived a person of his or her civil rights by using more force than the law allows, a standard that is challenging to prove in confrontations that unfold rapidly and when snap judgments are made.

In the Baltimore case, the six suspended officers have been on the force from three to 18 years.

Officer Garrett Miller, according to court documents, accused Gray of carrying a switchblade, which was discovered in Gray’s pocket after he was stopped.

The others are Lt. Brian Rice, 41;
Sgt. Alicia White, 30; officers

Caesar Goodson,

William Porter and Edward Nero.

The officers’ specific roles in the arrest were not released by city officials.