CHICAGO (AP) – Thirteen people were killed in protests on the first day of Democratic National Convention In Chicago, most of them related to a “brief breach” of the security fence “within sight and hearing of the United Center,” the city’s police chief said on Tuesday.

More protests were planned throughout the week, including one outside the Israeli consulate on Tuesday evening, but the turnout at the main rally on Monday was far below organizers’ estimates of more than 20,000 participants.

Chicago Police Commissioner Larry Snelling said Tuesday that the The audience number was around 3,500 strong and the vast majority of demonstrators were peaceful.

However, some clashed with police, using pepper spray against them and throwing water bottles at officers during the confrontation in the park, where there was a gap in the security fence, Snelling said. He said officers did not use chemical sprays.

“Our officers showed great restraint,” he said at a press conference. “We will not tolerate vandalism and violence in our city. … We will continue to protect the city.”

Snelling said that with more protests planned, his department is prepared to de-escalate the situation if possible.

“We are up to this challenge,” said Snelling. “The city is up to this challenge.”

The park where most of the arrests took place is a block from the convention grounds and served as the destination for a march of thousands demanding a ceasefire in the war between Israel and Hamas. Several dozen activists split off from the main group. broke through the fence, and were pushed back by the police.

Authorities said the internal security perimeter around the United Center had not been breached and there was no danger to convention attendees.

On Tuesday morning, additional fencing was erected in the park and high metal barriers were reinforced to prevent protesters from lifting and removing the panels. There were no police or protesters in the park early Tuesday.

The 13 people arrested during Monday’s protests were held on charges ranging from trespassing, resisting justice and obstruction of justice to aggravated assault against police officers, Snelling said.

At least ten of them were arrested in connection with the fence, he said.

Snelling said he did not associate those who tore down the fence with the entire march. He said the vast majority of participants were peaceful, and he praised his officers’ conduct in that moment.

The Chicago chapter of the National Lawyers Guild said two of those arrested were hospitalized. Snelling said they were taken to the hospital to ensure they received the medications they were taking.

In addition, two people were arrested for property damage and resisting state authority during a protest march on Sunday evening. By Tuesday morning, 15 people had been arrested.

In downtown Chicago, there was tighter security than usual – including police officers with guns slung across their bodies – outside the office building that houses the Israeli consulate and a major transportation hub for the city. Metal barricades were erected and an official said they were preparing for a 7 p.m. demonstration.

The consulate, located about 2 miles from the United Center, was the site of Numerous demonstrations since the Gaza war began in October. It is located in a building connected to the Ogilvie Transportation Center, a major commuter rail station.

Most of the largest demonstrations were organized by the coalition to march on the DNC, The campaign’s focus is on calling for a ceasefire in Gaza, but smaller protests took place throughout the city during the congressional welcoming party at Navy Pier.