It’s anyone’s guess how many at Donald Trump’s rally on Friday were there in opposition. Maybe a quarter. Maybe a third. However many, they clustered in UIC Pavilion’s northwest stands, farthest from the stage, though throughout the arena it was not hard to find women in hijabs sitting patiently amongst men in red baseball caps.

Save for the occasional disruption—instigated by whom was never clear—the mood was nervous but sedate. Boring, even.

Then at 6:30 p.m., instant pandemonium and astonishment. Claiming concerns for safety, Trump had canceled the event. No longer restrained by decorum, protesters danced and cried in jubilation, chanting “U-S-A! U-S-A!” One young man in a conservative suit and tie skipped across the arena floor, unbuttoning his shirt like Superman to reveal a “Black Lives Matter” T-Shirt.

Meanwhile, Trump supporters appeared stunned into silence. Just 15 minutes earlier they had been the ones chanting, gleefully cheering on security each time it was called to eject someone. Now, many were distraught. Others, furious. Some clenched fists,  but more clenched phones, documenting the experience.

It seemed unlikely the two groups could leave the stadium peacefully, but for the most part they did. It may as well have been the acrimonious aftermath of a Bears-Packers game. The day’s winners taunted and jeered at the losers; the losers seethed and promised payback. Rarely did confrontations escalate beyond ugly shouting and middle fingers. (Which is not to say there were not physical altercations. There were, and police made five arrests.)

Here's what we saw, starting from when people started entering the arena around 3 p.m.