Chicago Police issued a statement saying they did not consult with the campaign and had no part in the decision to cancel the rally. Neither did UIC Police.

"I met with law enforcement and I think we made the wise decision to cancel," Trump told CNN. "Our freedom of speech was violated totally, but I didn't want to see anybody get hurt. ... I made the decision in conjunction with law enforcement."

Ninety minutes later, Trump explained why he called off the rally.

The eagerly anticipated rally came undone at 6:30 p.m., a half hour after Trump was scheduled to take the stage at the University of Illinois at Chicago. One protester rushed the podium and tore up a Trump sign before two security guards pulled him off the stage.

Chants of "We stopped Trump" and "Bernie, Bernie" echoed through the arena. Trump supporters countered with "USA, USA, USA."

CHICAGO, IL — A Donald Trump rally in Chicago on the UIC campus was canceled over concerns about security as tension formed within the large crowd between Trump fans and foes. When the announcement was made from the podium Friday night, thousands of protesters cheered to celebrate having shut down Trump's rally.

As of 9 p.m., the streets outside the UIC Pavilion were clear of protesters. A small group of protesters lined up outside of the Trump International Hotel and Tower instead. The protesters, a collection of races, ethnicities and ages, were drawn to the Trump rally to protest the GOP presidential candidate's increasing rhetoric against immigrants and Muslims.

Just an hour earlier, however, several thousand people were still packed onto Harrison Street outside the arena, chanting, screaming and waving signs. Protesters marched toward I-290 with the apparent intention of getting on the expressway. Police blocked their path.

Thousands of anti-Trump protesters managed to get inside the UIC Pavilion.

"We don't want America to be seen around the world as a country of hate," Stephania Muzques, a college student, told Patch. "They all look at us and are baffled because of this. But we wanted to come here and help show the world that no, not everyone supports him."

One attendee who waited in line for hours noted that the event itself seemed poorly organized inside the UIC arena.

"What had been an orderly line mushroomed into an amorphous mob. The doors had opened at 3 p.m., and while thousands were already inside, as it turns out there was more room," wrote Matt Baron, a Chicago-area businessman, on his blog. "Whoever was in charge of the flow of would-be attendees didn't stick with it. Or maybe nobody was 'in charge'?

"Consequently, people who were strolling in the area could—and did—simply jump into the crowd at this last stage. The crowd was gradually pressing in, and an undercurrent of danger began creeping in, along with collective resentment and restlessness."

When the cancelation announcement was made over the loudspeakers — "... for the safety of all the tens of thousands of people that have gathered in and around the arena tonight's rally will be postponed until another date. Thank you very much for your attendance, and please go in peace," a man said — some tempers flared and fists flew as Trump backers and protesters got into each other's faces.

Trump supporters were clearly disappointed they did not get to hear Trump speak. Some traveled hundreds of miles to get to Chicago.

"We came to hear him talk, but this was all shut down because we don't have freedom of speech," one woman freely shouted to everyone in general and no one in particular. "There's no freedom of speech in America!"

One police officer injured in the scuffling was seen walking outside the arena at the intersection of Van Buren and Racine with blood streaming down his face. Police said four officers were hurt Friday night.

Witnesses said much of the conflict in Chicago Friday night was initiated by the protesters, not the Trump supporters.

"I think we have a very divided country," Trump told CNN.

Protesters also demonstrating behind police barricades outside of #Trump Tower in Downtown Chicago. pic.twitter.com/nHVBOSgpN4 — Bill Ruthhart (@BillRuthhart) March 12, 2016

At least half a dozen people were taken into police custody, according to witnesses, including one man who was bloodied by a police baton. CBS News reported that one of its reporters was detained by police.

A CPD spokesman released a statement:

"We are continuing to work with our partners in the United States Secret Service and the University of Illinois at Chicago Police to protect people's First Amendment rights and ensure everyone is able to disperse the area safely."

Trump told MSNBC the images of the chaos at his rally could spur greater voter turnout on Tuesday when Illinois, Ohio, Florida, Missouri and North Carolina conduct primaries. Trump also said he "can't even have a rally in a major city anymore."

"Whatever happened to the right to get together and speak in a very peaceful manner?" he asked.

Trump also talked to Fox News.

"You can't even have a peaceful rally today in a major city in the United States, which is a terrible thing. But you know, Chicago is the home to some pretty rough rallies," Trump said, pointing to the 1968 Democratic Convention. "A lot of people hurt, a lot of people killed. I didn't want to see anything like that happen."

President Barack Obama late Friday, speaking at a Democratic National Committee gathering in Texas, addressed the Trump campaign rally episodes, the worst of which has now unfolded in the president's own hometown.

"What's happening in this primary is just a distillation of what's been happening in their party for more than a decade," Obama said, according to a report filed by the Texas Tribune.

GOP presidential candidate Ted Cruz, also in Illinois Friday to speak with suburban Republicans at a Lincoln Day Dinner in Rolling Meadows, said Trump deserves a share of the blame for conflict at his rallies.

"When you have a campaign that affirmatively encourages violence ... that is facing allegations of physical violence against members of the press, you create an environment that only encourages this sort of a nasty discourse," Cruz said. "Today is unlikely to be the last such incident."

Meanwhile, Democratic candidate Bernie Sanders spoke in Chicago's south suburbs, gathering more than 9,000 supporters at Argo High School in Summit. Much like the Trump rally, thousands of people lined up outside the school to get in and waited hours to do so. The line stretched a mile down the street.

The mood there was considerably different than the one inside and outside the Trump rally.

"We're not going to let Donald Trump or anyone else divide us," Sanders told the crowd.

Sanders also drew attention to Trump's divisiveness but did not mention the rally protests.

"We do things a little different in this campaign: We bring people TOGETHER," Sanders tweeted during the Trump rally chaos.

After speaking, Sanders sang the famous Woody Guthrie folk song "This Land is Your Land" from the stage, linked arm in arm with supporters.

(There's some historic irony in that moment, too, as Guthrie has a connection to Trump. Not Donald but his father, Fred. The elder Trump was the folk singer's landlord, and Guthrie despised him for his ruthless tactics in exploiting black tenants. "I suppose Old Man Trump knows just how much racial hate he stirred up," Guthrie once wrote.)

Attitudes about race, hate and bigotry were at the root of Friday night's tension at the Trump rally.

Protesters and Trump supporters began yelling at each other, shoving and throwing up middle fingers immediately after the announcement to cancel around 6:30 p.m. Police waded into the crowd inside the arena to separate people. Fights then began breaking out. Hundreds of Chicago Police officers were deployed to the scene in advance. More Chicago Police, State Police and UIC Police were deployed into the area. Police lined up en masse on aisles in the arena to push people out of the venue.

Chanting anti-Trump protesters blocked the entry to a parking garage as the arena was evacuated. Witnesses claim some protesters were beating on cars in the parking garage with hammers, but this has not been confirmed.

Anti-Trump protesters lined up for block after block around the arena Friday night. Outside the arena, protesters began jumping up and down on police cars in celebration. As of 7:30 p.m., the scene outside had calmed considerably. By 8 p.m., the parking garage was emptied of both cars and protesters.

Earlier in the day, reporters took note of the interesting signs, placards and t-shirts displayed by the protesters.

"Mein Trumpf," read one which included an image of Trump in KKK robes.

"We shall overcomb," was etched on a t-shirt worn by a little girl, a pun on Trump's unusual weave of hair.

"Bigotry is Unpatriotic," read another.

Here's a Trump supporter and a protester having an open/honest convo. @DNAinfoCHI pic.twitter.com/fvbVvu1XJv — Evan F. Moore (@evanFmoore) March 12, 2016

Demonstrators infiltrate and shut down rally of political campaign they view as intolerant. Pot meet kettle? #TrumpChicago — David Shuster (@DavidShuster) March 12, 2016

Trump supporters began lining up at 3 a.m. Friday to get into the arena. Trump was already 30 minutes late getting to the arena when the postponement was announced. The GOP frontrunner never took the stage.

The UIC Pavilion holds 10,000 people. Protest groups indicated they could bring as many as 15,000 people to the campus to rally against the policies and positions Trump has espoused during his campaign — including deporting Mexicans, building a wall on the U.S.-Mexican border, and barring all Muslims from entering the United States.

Many protest groups, including college students, African-American organizations, Mexican groups and Muslim organizations organized efforts to bring people to the campus to protest this rally.

Prior to the scheduled start time, as Trump supporters entered the arena, some were seen chanting and taunting the protesters: "Trump! Trump! Trump! Illegals are Illegal."

When Trump announced he would host a campaign rally in Chicago and rented out the UIC arena, students and faculty balked. Faculty sent a letter to the administration saying the campus was not a suitable place for such an event and asking for the rally to be canceled. A student group started a petition, which focused on safety and security concerns, which was signed by more than 40,000 people.

It was clear in the days preceding the event that protesters were spoiling for a confrontation with the Trump supporters after weeks of Trump fans going after protesters at rallies in other cities.

Trump has encouraged his supporters to get rough with protesters, too, telling them "don't worry, I'll pay the legal bills."

Throughout the week, Trump has been criticized by fellow Republicans for not discouraging his supporters from attacking protesters at his campaign rallies. The criticism intensified after a 78-year-old man punched a protester in the face a few days ago

Earlier Friday in St. Louis, Trump said of protesters at his rallies, "These are not the people who made our country great."

Sign says "Undocumented un afraid." Both of them were kicked out #trump #chicago pic.twitter.com/w8uyhfBIfb — Yoav Gonen (@yoavgonen) March 12, 2016

The scene right now at the Trump rally in Chicago is surreal. Hard to believe what I'm watching is happening in America. — Brendan Boyle (@RepBrendanBoyle) March 12, 2016

Donald Trump Chicago rally cancelled amid security concerns https://t.co/fY5QvtXX6n via @WGNNews — Brett bside Matthews (@iamthebside) March 12, 2016

Couple kids from Aurora playing Trump the board game. "It's like Monopoly but better cause it has Trump" kid said. pic.twitter.com/ippdwRNnQH — Joe Ward (@JayDubWard) March 11, 2016

Also on Patch