By Natalie Sherman, Chris Kaltenbach and Matt Pearce

A 25-year-old Baltimore man died Sunday a week after reportedly suffering a partially severed spine during an arrest, and the mayor vowed "to find out exactly what happened" and "hold the right people accountable."

Baltimore police, working in conjunction with the state attorney's office, had launched a criminal investigation into the April 12 arrest of Freddie Gray last week.

According to a police timeline, Gray was conscious and talking when officers put him into a police van after his arrest, which they said came when he ran from four bicycle officers. Less than an hour later, police summoned paramedics to take Gray to the hospital, according to the timeline.

Police haven't said what crime Gray was suspected of, nor how he sustained his injuries. A brief witness video of the end of the arrest, obtained by The Baltimore Sun, showed officers carrying Gray toward a police van as his legs dragged on the ground. In another witness video that aired on the local CBS affiliate, WJZ-TV, he could be heard screaming.

The officers involved have been placed on administrative leave.

An attorney representing Gray's family, William H. "Billy" Murphy Jr., called Gray's injuries "catastrophic."

"What we know is that while in police custody for committing no crime _ for which they had no justification for making the arrest except he was a black man running _ his spine was virtually severed, 80 percent severed, in the neck area," Murphy said in a statement Sunday.

Gray "lapsed into a coma, died, was resuscitated, stayed in a coma and on Monday underwent extensive surgery at Shock Trauma to save his life," Murphy's statement said. "He clung to life for seven days and died today at approximately 7 a.m. We believe the police are keeping the circumstances of Freddie's death secret until they develop a version of events that will absolve them of all responsibility."

Shock Trauma Center is a hospital affiliated with the University of Maryland Medical Center.

Gray's sister, Carolina, called for the officers to face criminal charges.

"The officers who did this need to be arrested now, locked in jail and charged with murder," she told the Guardian. "And this all needs to be investigated by separate police. How can Baltimore police look into their own?"

"He's gone," Gray's stepfather, Richard Shipley, told The Sun. "What else is there to say?"

Police have assembled a task force to investigate the arrest. An independent board also will review the administrative case against the officers after State's Attorney Marilyn Mosby decides whether to file criminal charges. A spokeswoman for Mosby could not be reached Sunday.

Deputy Police Commissioner Jerry Rodriguez said the reason for Gray's arrest was still "a bit vague," other than that Gray was in a high-crime area and that officers suspected Gray was "immediately involved or had been recently involved in criminal activity."

Rodriguez said police "have no physical, video or any other evidence of an altercation" that would have resulted in Gray's injuries.

Baltimore Mayor Stephanie Rawlings-Blake extended condolences to Gray's family in a statement issued on Twitter. "Right now we are still collecting details surrounding this incident, but I want our residents to know that we will get answers," she added.

"This will be a transparent process, but our primary focus is to provide a prompt and comprehensive understanding of this incident," Rawlings-Blake said. "I want to let people know that we will find out exactly what happened, and we will hold the right people accountable."

Police Commissioner Anthony W. Batts also extended sympathy. "I have no words to offer that will ease the pain that has resulted," he said at a news conference with the mayor.

"All lives matter," Batts added in a nod to the "Black Lives Matter" mantra of protesters after recent incidents across the country that have resulted in the deaths of black males during confrontations with police.

More than 100 protesters have gathered for two days outside a Baltimore police station to demand answers about what happened to Gray.

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

(Sherman and Kaltenbach reported from Baltimore. Pearce, a Los Angeles Times staff writer, reported from Los Angeles. Colin Campbell, Sean Welsh and Justin Fenton in Baltimore contributed to this report.)

(c)2015 The Baltimore Sun