They set upon him. Beaten and bloodied, the unidentified man was saved, in a manner, by militiamen who dragged him through the crowd under metal shields, bundled him into the back of a car and drove him off at speed to an unknown fate.
No one could say what he'd done; he was a "provocateur", a term used by both sides of Ukraine's increasingly bitter divide to describe the other, but in the rebel-held east it means only one thing - a supporter of the "Fascist" government in Kiev.
It was a brutal picture of the mob-rule that has descended upon this city in eastern Ukraine, the biggest to fall to an armed uprising against a government in Kiev that wants to take the country west. Kiev blames Russia for fomenting the violence, a charged denied by Moscow.
Pro-Russian separatist leaders want a referendum on May 11 to declare Donetsk and the surrounding region an independent republic.
Whatever the outcome, it won't be recognized by Kiev. The anger unleashed in the process will prove hard to rebottle, and points to a state descending into dangerous disorder, potentially civil war.
"We will not forgive Odessa!" the crowd chanted, a phrase that has quickly become the new rallying cry in towns across Ukraine's industrial east.
The deaths of more than 40 pro-Russian activists in a burning building during clashes in the Black Sea port on Friday have injected new venom into the fight for Ukraine.
Sixty-seven pro-Russian activists, detained by police during the unrest, were busted from prison on Sunday by a crowd that broke down the main gate.
The cry was first heard in Donetsk on Saturday, when a couple of hundred people smashed up the city's state security building as evening fell, then walked down the street and ransacked the business headquarters of the region's Kiev-backed governor, steel baron Serhiy Taruta.