SAN JOSE (CBS / AP) — San Jose city officials Friday condemned violence that took place at Donald Trump’s campaign rally Thursday night that left some people bloodied, led to four arrests and injured a police officer.

Trump supporters leaving the presidential candidate’s rally in San Jose were pounced on by protesters, some of whom threw punches and eggs.

A dozen or more people were hit and car windows were broken. Trump hats grabbed from supporters were set on fire on the ground. At least one woman was pelted with an egg.

Police stood their ground at first but after about 90 minutes moved into the remaining crowd to break it up and make arrests. At least four people were taken into custody.

Police said that about 300 to 400 protesters gathered outside the presumed Republican presidential nominee’s rally that was expected to draw 12,000 to 15,000 supporters and started at 7 p.m. in the South Hall of the San Jose Convention Center.

A police officer suffered a minor injury to his wrist when someone threw a metal object at the officer and three people were arrested for assault with a deadly weapon. One person was arrested for unlawful assembly, police said.

“What happened last night was disgraceful,” San Jose police Chief Eddie Garcia said Friday afternoon at a news conference.

Garcia said police will never condone violence and assaults are not a First Amendment right.

Garcia is forming a five-person task force to investigate the violence and police will be working with the Santa Clara County District Attorney to prosecute the people who were violent.

Garcia defended his officers who he said protected thousands of Trump supporters who went home safely.

When questioned by reporters about officers holding to their crowd control lines rather than breaking away and stopping acts of violence, Garcia said officers had to determine whether the act was a life and death situation.

He said officers did not stop some acts of violence because arresting the perpetrators might cause more violence as protesters turned on police.

“That’s always a concern,” San Jose Police Officer’s Association spokesman Tom Saggau said.

When Garcia was asked what police could do differently next time, he said, “We would need more officers” with the goal of keeping more people from each other.

Garcia said about 250 officers were on duty for the event.

“This was an all hands on deck” event, he said.

But there was plenty of criticism leveled at police.

Social media lit up with angry tweets. Twitter user Steven Rodgers called for the chief to be fired.

Meanwhile Trump America called for a San Jose boycott.

One Trump supporter said his rights were taken away.

“People have the right to make their choices without the fear of violence, and this feels like a very violent situation,” said San Jose resident David Willis.

Saggau said San Jose does not have enough officers to handle an event such as Thursday’s rally.

A number of videos posted on social media showed violence between protestors and the business mogul’s supporters. Most of the violence took place at the end of the event, police said.

No significant property damage was reported.

But Saggau praised a separate peaceful protest held ahead of Trump’s rally. That protest was organized by a coalition of groups including Service Employees International Union Local 521 and the South Bay Labor Council.

That rally kicked off at about 5:30 p.m. a block from the convention center at Plaza de Cesar Chavez at 194 S. Market Street. Protesters held signs that said “Trump leave San Jose” and “Do not forget who picks your food! Remember America was built by immigrants,” in response to Trump’s anti-immigration rhetoric.

SEIU Spokesman Stephen Boardman could not say how many union members were there, but said it was not a union-wide effort.

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Trump held a rally Friday afternoon at the airport in the much smaller and more conservative city of Redding, where the high temperature could reach 102 degrees. Redding, far away from the large urban areas of San Francisco and Sacramento, and the anticipated triple-digit heat could make for a smaller and less active crowd.

Thursday night’s crowd, which had numbered over 300 just after the rally, thinned significantly as the night went on, but those who remained near the San Jose Convention Center were rowdy and angry.

Some banged on the cars of Trump supporters as they left the rally and chased after those on foot.

Mayor Sam Liccardo, a Democrat and Hillary Clinton supporter, criticized Trump for coming to cities and igniting problems that local police departments had to deal with.

“At some point Donald Trump needs to take responsibility for the irresponsible behavior of his campaign,” Liccardo told The Associated Press by phone.

Liccardo issued a statement about the violence Friday, saying, “San Jose police officers performed admirably and professionally to contain acts of violence and protect individuals’ rights to assemble, protest and express their political views. While it’s a sad statement about our political discourse that Mr. Trump has focused on stirring antagonism instead of offering real solutions to our nation’s challenges, there is absolutely no place for violence against people who are simply exercising their rights to participate in the political process.”

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Clinton and Democratic opponent Bernie Sanders will also make campaign stops in the state on Friday in California as they look to Tuesday’s state primary.

Trump, the presumptive GOP nominee, spoke for about 50 minutes at the rally, sniping at Democratic candidate Hillary Clinton and calling her speech on foreign policy earlier in the day “pathetic” and “sad to watch.”

Protesters before the speech included Adam Rivas, a 22-year-old community college student who was born and raised in San Jose. He was holding a spray-painted sign that read “Dump Trump.”

Rivas said he was particularly disturbed by Trump’s remarks about Mexicans.

“For any one Mexican here he bashes, there are about 20 Mexicans out there who are hard-working and just doing their job,” he said.

Trump supporter Debbie Tracey, a U.S. Navy veteran from San Jose, said she came to hear Trump speak, and left his rally with two hats, a T-shirt and a handful of signs that said “Veterans for Trump.”

Passing in front of a wall of protesters, many chanting in Spanish, she said she supported Trump’s call for a wall along the U.S.-Mexico border.

“I’ll go help build the wall because if you are going to come to this country, land of opportunity, you should be here legally,” she said.

Trump was last in the Bay Area in late April to speak at the California Republican Convention in Burlingame.

Protesters blocked the hotel where Trump spoke and the candidate had to traverse a ditch and enter the hotel through a back door. Five arrests and a minor injury were reported during the protest at the convention.

San Jose police are asking the public to submit any video or information they have that will help police arrest and prosecute the people who were violent.

Anyone with video to share has been asked to call (408) 537-4161 or 311. People who want to remain anonymous can call Crime Stoppers at (408) 947-7867 or go to https://www.p3tips.com/tipform.aspx?ID=504. People can also file a crime report at http://www.sjpd.org/ReportingCrime/OnlineReport/.

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