The masked vandals who caused up to $100,000 in damage in Hamilton on Saturday night were organized and likely planned their actions ahead of time, police said Monday.
Around 30 people assembled in a city park before marching down a busy street, hurling rocks through shop windows and at people's homes, police said.
"We know this is not a spontaneous act committed by these people," Insp. Paul Hamilton said. "This was very well planned, very well executed."
Members of the group carried a banner with them that read, "We are the ungovernables."
"I can't give you a name for this group and we haven't identified anybody yet," Hamilton told reporters on Monday.
Vandals wore multiple layers of clothing that took off to change their appearance as they fled the scene – a common tactic at major demonstrations, he said.
An event billed as the Southern Ontario Anarchist Bookfair took place in downtown Hamilton over the weekend, the inspector said.
"I'm not connecting this to the bookfare specifically, but like-minded people attended that event from right across the province, so we are investigating the possibility that there are people from outside this community that committed these acts," he added.
Police initially received calls about people causing "mischief" in the park Saturday night. The two or three officers who arrived at the scene were "not prepared for 30 or so adults, so they had to retreat and call for backup," Hamilton said.
The group scattered, some of them getting into vehicles, when about 30 officers from various units showed up, police said.
Hamilton called on witnesses, and even vandals themselves, to speak to police.
"Not everybody threw rocks at windows that night, so maybe there's somebody in that group that doesn't agree with the philosophy of this group and what took place," he said. "We really hope that one of those people would step forward and provide us with some information."