Updated at 2:40 p.m.

Boston Mayor Marty Walsh and Police Commissioner William Gross on Monday defended both the peaceful protesters who gathered by the thousands in downtown Boston Sunday and the police who responded to a wave of violence and looting that followed the demonstrations.

“I don’t want anything to take away from what they accomplished and the impact that they had yesterday,” Walsh said, speaking of the estimated 20,000 people who gathered to protest police brutality and the killing of George Floyd by Minneapolis police officers. “I want to say to all those peaceful demonstrators: Your words, your testimony, your call to action moved me and you are moving our society forward.”

But he added, “What happened in downtown after the protest was an attack on those values and it was an attack on our city and its people.”

Clashes between protesters and police erupted late Sunday as the demonstrations were dipersing. Several police cars were set on fire, windows were smashed and shops were looted on several blocks around the Boston Common. Walsh, Gross and other local officials held a press conference Monday to respond to the violence.

Walsh said nine police officers were taken to the hospital and dozens were treated in the field.

Gross said there were 53 total arrests Sunday night — with 24 of those arrested were from outside Boston, including two from out of state.

“It was rough for a while out there last night as the officers were attacked,” Gross said, but police stood their ground, with the conviction that “this is not going to happen — no one is going to take over our city and burn it to the ground.”

Walsh said the demonstration wound up being much larger that first expected.

“When you have marches there’s always some agitators in the crowd, and it’s is usually a handful. Last night it was more than a handful,” he said.

Walsh praised the Boston Police Department's approach to yesterday's protests. The day’s demonstrations went on without incident until “the police had to be activated when it got violent last night,” he added.

But some protesters blamed the police for the outbreak of violence.

Jamie Berg, a student in her last year at Emerson College who participated in the protest, told WGBH News, “Last night the protests were entirely peaceful and they started tear gassing everyone without notice, without warning, and they surrounded the Common. It was absolutely disgusting.”

She said the peaceful demonstration was met by police with much more force than groups of visibly armed protesters who have rallied around the country in opposition to coronavirus shutdowns.

Her friend Evan McDonald, a recent Emerson graduate, said the police clamped down on the protesters.

“We were walking down Tremont, our hands were up — the police, they flanked us,” he said. “They closed off the access to the red and the orange lines.

“A lot of people couldn’t go home,” McDonald added. “We didn’t know where to go.”

Walsh did not comment on the closures, saying that was a decision taken by MBTA when “it got a little scary” at the Downtown Crossing area.

Suffolk County District Attorney Rachael Rollins, who also spoke in front of City Hall Monday, expressed the most sympathy with the outrage behind Sunday night's mayhem.

Black people “have looked around this country and seen police officers … shoot us down in the streets as if we were animals,” she said.

She added that though she does not wish harm on any Boston police officers who showed up to do their jobs, “this burning rage that you are seeing when you turn your TV on or you hear in my voice is real.”

“It is completely ironic,” Rollins continued, “to have to say to you, ‘Please don’t be violent. Please keep your voice down. Please be silent and comply with all of the police’s requirements.’ When in fact, it's those very people that murder us with impunity. But that’s where we are right now.”