Reuters –  Baltimore police vowed on Monday to make a full and swift probe of the death of a black suspect who suffered spinal injuries after white officers arrested him, the latest incident to raise questions about the treatment of minorities by U.S. police.

Freddie Gray, 27, of Baltimore, was arrested on April 12 and died on Sunday from a spinal injury after slipping into a coma, officials said. His death has sparked outrage and protests in the largely black Maryland city of about 625,000 people.

Deputy Police Commissioner Jerry Rodriguez said officers had arrested Gray without using force after he fled when they approached him. They put him into a police van to take him to a station, he told a news conference.

"I know that when Mr. Gray was placed inside that van, he was able to talk, upset, and when Mr. Gray was taken out of that van, he could not talk and he could not breathe," Rodriguez said.

Police Commissioner Anthony Batts said a wide-ranging and transparent department investigation would be concluded by the end of next week and the results forwarded to state prosecutors. After that, the probe will undergo an independent review, he said.

"We will examine every piece of evidence, and we will go wherever the evidence takes us," Batts said.

He said the Baltimore police would institute training and reforms on the transport of suspects and their medical treatment.

Six officers involved in the arrest were suspended with pay, the New York Times reported.

Gray's death followed the killings of a number of unarmed black men by white police officers, including in Ferguson, Missouri, and New York. The deaths have raised a outcry over the treatment of minorities, and particularly the use of force, by law enforcement.

Police have said Gray had a switchblade knife in his pocket when he was arrested.

The cause of the spinal injury was unknown, Rodriguez said. A lawyer for the Gray family, William Murphy Jr., said on Sunday his spine was 80 percent severed at the neck while in police custody.

Gray asked for an inhaler when he was placed in the van, and the van made two stops on the way to the station. A second suspect was put in the vehicle but was separated from Gray by a metal barrier, Rodriguez said.

Batts and Mayor Stephanie Rawlings-Blake, both of whom are black, appealed for calm.

"Our community is experiencing a great deal of trauma, and none of us get the answers that we need or that the Gray family deserves by resorting to violence," Rawlings-Blake said.

A video taken by a bystander showed officers dragging Gray into the van. Police also released an unedited street surveillance video showing the arrest.

The U.S. Justice Department is conducting a separate review of complaints about Baltimore police, at Batts' request. It followed a Baltimore Sun newspaper investigation that found the city had paid almost $6 million since 2011 to settle more than 100 lawsuits alleging police brutality and other misconduct.

The city has long struggled with high crime rates, and last year imposed one of the strictest youth curfews in the United States, an effort to reduce the frequency of petty crime. That measure has met criticism from local residents who say it is unevenly enforced.

A few dozen demonstrators gathered outside city hall in a protest organized by the leftist Peoples Power Assembly, according to a WMAR television, an ABC affiliate.

"If we stay calm at a time like this there is something wrong with us," one demonstrator said. Protesters carried signs that said "Freddie Gray Justice" and "No Justice No Peace."

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