BALTIMORE: Thousands of protesters took to the streets to demand answers in the case of Freddie Gray, the largest rally since the 25-year-old black man died in police custody.

After hours of peaceful demonstrations, pockets of protesters smashed police car windows and storefronts. Saturday's protests came a day after Deputy Commissioner Kevin Davis said Gray should have received medical attention at the spot where he was arrested, before he was put inside a police transport van handcuffed and without a seat belt, a violation of the department's policy.

Gray died April 19 after suffering a fatal spinal injury while in custody.

His death has intensified a national debate over police treatment of African-Americans.

Authorities have not explained how or when Gray's spine was injured.

Video showed him being dragged into a police van, and police have said he rode in it for about 30 minutes before paramedics were called.

Gray's death has been compared to those of other unarmed black men who died at the hands of police in New York City and Ferguson, Missouri. Residents voiced their anger Saturday at how the department and the city's officials are handling the investigation into Gray's death.

Protesters threw cans and plastic bottles in the direction of police officers. One protester broke the window of a police cruiser, grabbed a police hat inside and wore it while standing on top of the cruiser with several other protesters.

At least two people were hurt in the mayhem, and at least a dozen were arrested. In her first public comments since Gray's death, his twin sister, Fredricka Gray, appealed for calm. “My family wants to say, can you all please, please stop the violence?” she said at a news conference with the mayor. “Freddie Gray would not want this. “

Earlier Saturday, the crowd paused for a moment of silence in front of Shock Trauma, the hospital where Gray died. Signs in hand, with slogans such as “Jail Killer Police!” and “Unite Here!,” demonstrators filled two city blocks and marched to City Hall, where the crowd overtook a grassy plaza.

Tanya Peacher, a 36-year-old Baltimore resident, said she'd never attended a protest in the city before, but watching a video of Gray's arrest motivated her. “I looked at my son,” she said, “and thought, 'That is my son. “'

At a downtown intersection, a dozen marchers laid down in the street during an impromptu “die-in. “ Both Commissioner Anthony Batts and Mayor Stephanie Rawlings-Blake, who took office in 2010, are African-American.

They came in making promises to the inner-city residents and police who spent decades staring each other down in neighborhoods ravaged by crack and heroin.

But with each death of a black man in custody, their efforts to overcome mistrust have hit hard walls of skepticism and outrage.

Batts says he's fired 50 police employees and reduced officer-involved shootings, and the use-of-force reports police must file dropped from 598 in 2012 to 435 in 2014.

But he acknowledged that some cases have “tarnished this badge and the reputation of the department. “ Gray is at least the fifth black man to die after police encounters since Batts took charge.

A Baltimore Sun investigation revealed last year that the city has paid roughly $5.7 million in brutality settlements since 2011, involving 102 instances of excessive force. Batts then asked the US Justice Department to review the department's policies and procedures.

Now the Justice Department has opened a second probe, by its Civil Rights division, examining Gray's death. Baltimore had one of the nation's busiest markets for heroin and crack cocaine when Martin O'Malley ran for mayor in 1999.

The future Maryland governor and Democratic presidential candidate imposed a “zero tolerance” policy that did reduce crime, but it also resulted in thousands of arrests without cause. In 2010, civil rights groups the ACLU and NAACP reached an $870,000 settlement with the city that required police to track their arrests.

But by 2012, an independent auditor found Baltimore officers still couldn't justify 35 percent of their arrests.