Baltimore's mayor promised accountability Monday following the death of a man in police custody.
Cell phone video shows the moments after Freddie Gray was arrested. He died Sunday, a week after his arrest. Lawyers say his spine was nearly severed.
CBS News correspondent Mark Albert reports his lawyers accuse police of covering up what happened.
Freddie Gray's screams can be heard on the cell phone video that CBS Baltimore obtained from his family. It shows white Baltimore police officers lifting and carrying Gray, his feet dragging on the ground. The officers put him into a police van where, authorities say, he was placed in "additional restraints."
About 30 minutes later, after the van arrived at a nearby police station, someone called an ambulance. By then, Gray was critically injured.
His lawyer says Gray's spine was 80-percent severed at his neck, his voice box partially crushed.
After being in a coma for a week, the 27-year-old died on Sunday.
Protests have steadily grown, including a march over the weekend to the Baltimore police station where Gray was taken.
Police Commissioner Anthony Batts tried to reassure protesters Sunday, saying: "All lives matter. All lives matter in this city."
Police extended their condolences to the gray family, but have not yet told them - or the public - how Gray became so severely injured, exactly why four bicycle officers stopped Gray in the first place, or why he ran from them.
According to reports, Gray has a history of drug offenses, and police say he was in a high-crime area known for drug incidents.
"The officers believe that Mr. Gray was immediately involved or recently involved in criminal activity and decided to make contact with Mr. Gray," Deputy Police Commissioner Jerry Rodriguez said.
Baltimore's mayor, Stephanie Rawlings-Blake, also provided no answers on Sunday, but promised transparency once the investigation is over.
"I want citizens to know exactly how it happened, and if necessary I will ensure that we will hold the right people accountable," she said.
In a statement, Gray's attorney told CBS News police do have video of the arrest, and accused the department of withholding it to hide the facts.
The police commissioner has promised not only an internal investigation, but an independent probe as well. The Department of Justice is already investigating the Baltimore Police Department after a string of brutality cases.