The vandalism occurred after most of the tens of thousands of jubilant hockey fans left the area.
Looters wrapped their faces in garments — in some cases the ones they'd stolen — and dashed into a liquor store. With their identities concealed, they leaped through the smashed front window and emerged moments later with their arms full.
One man warned his female friend to be careful with the loot.
"Hide the bottle," he snapped. "The police."
He was referring to the line of officers who watched impassively from the closest street corner. Their reinforcements were on the way.
Rows of black-clad riot officers charged in from the peripheries, rattling their shields as a warning to the crowd before firing tear-gas canisters. Police said about 25 people were arrested and two officers sustained minor injuries.
Shortly after the Canadiens' 5-2 victory over the Penguins, fireworks erupted over St. Catherine Street as people crowd-surfed and held aloft trinkets, including Stanley Cup replicas and a stuffed penguin.
The flag-waving crowd was as euphoric as the 21,000 fans who crammed into the Bell Centre to watch the game on giant screens. After the game, they spilled out into the streets chanting, "We want the Cup! We want the Cup!
Montreal has a history of hockey-related violence.
Cars were burned and downtown stores were trashed and looted after the Canadiens beat Boston in the 2008 playoffs, and there also were riots after Montreal's Stanley Cup victories in 1986 and 1993. The most famous riot was in 1955 when Habs great Maurice Richard was suspended and fans took to the street to cause such havoc that Richard had to make a public appeal for calm.