(CBS) — The Donald Trump rally at the UIC Pavilion was abruptly “postponed” Friday evening, amid security concerns, as protesters massed outside the University of Illinois-Chicago campus venue and even infiltrated the campaign event.

The announcement came around 6:30 p.m., after thousands of Trump supporters filed into the hall at Racine and Harrison, in anticipation of a speech by the controversial Republican presidential candidate. Protesters had marched across the University of Illinois-Chicago campus toward the site of the campaign rally.

Trump said his campaign made the decision after meeting with law enforcement officials. Chicago police said they did not meet with the Trump campaign. “Nor did we make any suggestion the event be cancelled.”

“I felt it was just safer. I don’t want to see anyone get hurt,” Trump told MSNBC’s Chris Matthews following the pullout.

Matthews pressed Trump about the unrest displayed by a diverse group of protesters.

“There’s a lot of anger in the country, and that’s sad to see,” the candidate replied.

He said he would come back to Chicago “some other time.”

Things were tense outside, following the announcement inside the UIC Pavilion, as throngs of anti-Trump demonstrators ringed the building. A Chicago police officer was seen bleeding from the head, but it wasn’t immediately clear what had happened; he was reportedly taken to Stoger Hospital in good condition. Other police officers could be seen clashing with demonstrators.

According to Chicago Police News Affairs, two officers received minor injuries and five people were arrested.

Police rushed from their posts outside the UIC pavilion where they found officers struggling with a protester. Eventually the protester was subdued on the pavement of a nearby intersection, but not before being bloodied in the melee. A handful of other activists were also seen taken away by police.

The announcement of the event’s cancellation drew a mixed response at UIC Pavilion, CBS 2’s Mai Martinez reports. A number of protesters inside the venue were elated, while Trump supporters were disappointed and angry. Police shooed everyone out, while trying to keep peace.

One protester told CBS 2 he thought the campaign was shut down because Trump was “scared.” When asked who Trump was scared of, the protester replied, “Of us!”

Outside of the event, chopper video from CBS 2 showed hundreds of people gathered at an intersection. Others tried to form human chains attempting to block traffic, however, police were able to quickly push the crowds to disperse.

Eventually, the protesters were cordoned off to an area outside the campus parking garage, where police cleared a path for attendees to leave. Hundreds of protesters stood along the road taking part in chants and holding signs. One held a sign that read: “Has Humanity Ever Built A Wall That Could Withstand Human Will?”