Batts said Friday that Gray was not buckled in a seat belt while in the police van, which is a breach of protocol, and that "our police employees failed to give him medical attention in a timely manner multiple times."
Batts urged protesters to await the findings of a police investigation before making any conclusions, adding, "If someone harmed Freddie Gray...they have to be held accountable."
His comments were criticized by the Baltimore Fraternal Order of Police Lodge 3, a police officers' union, as "politically driven, and in direct contrast to the commissioner's own request not to jump to any conclusions."
Protesters began Saturday’s action at the Western District Police Station, near the site where Gray was arrested, before marching toward City Hall. Participants shouted slogans denouncing police brutality and carried black and yellow placards that read: “Community control of police now!,” “Jail killer police!” and “Unite Here!”
The racially diverse group of protesters said their goal was to demand justice for Gray and call attention to the ongoing problem of police brutality.
"We're tired of this, what is going on with this police department," said Justice Allah, a protester and member of Black Lawyers for Justice. "We're tired of our mayor turning a blind eye."
Makayla Gilliam-Price, a Baltimore resident, said it was important that city residents rally in support of the Gray family.
“If nothing else, it’s therapeutic for the community,” she said.
Another protester, who declined to give his name, told Al Jazeera the action wasn’t specifically about Gray, but the criminalization of black men in general.
“This ain’t just Freddie, this is the brother in New York, this is the brother in Ferguson — it’s all the brothers,” he said. “There’s only so many times you keep smacking someone in their face before they get fed up with it.”
The Baltimore Police Department on Friday released photos and surveillance video of Gray’s arrest, which appeared to inflame passions even further — with many protesters vowing to “shut down” Baltimore.
Officials said police would complete their investigation into the case by May 1 and turn over their findings to state prosecutors to be followed by an independent review. Meanwhile, six police officers involved in the case have been suspended.
The U.S. Department of Justice is conducting a separate probe into Gray's death. A wake for Gray is scheduled for Sunday, with his funeral to be held on Monday.
Al Jazeera and wires services