BALTIMORE — Amid tears and cries for justice, demonstrators poured into the streets of Baltimore carrying signs emblazoned with the name of a man who died from a spinal injury he suffered while in police custody. Tuesday’s demonstration marked the beginning of a week of protests and rallies planned across the city.

The Justice Department said earlier in the day that it has opened a civil rights investigation into the death of Freddie Gray, a 25-year-old 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.

At the site of Gray’s arrest, more than a thousand demonstrators gathered to remember Gray, who friends and relatives said was kind, funny and generous, and to call for police reform.

“I want this to be a sign to the Baltimore Police Department that this is not an act of surrender,” said the Rev. Jamal Bryant of the Empowerment Temple, one of the rally’s organizers, as he called on those in the crowd to raise their hands. “It’s a sign of strength, of one unity and one commitment that we will not rest until we get justice for Freddie Gray.

“The world is watching,” Bryant said. “The world is watching, and the world needs to see that black Baltimore is unified.”