When Montreal hockey fans rioted in 1993, downtown merchant Jean-Jacques Trudel installed a metal grill on the front of his electronics store. When looters rampaged in 2008, he put steel reinforcements on his broken plate-glass windows.
On Thursday, he arrived at his centrally located store to find his grill bent and glass on the sidewalk. And like many Montrealers, he wondered why hockey triumphs seem to end in clouds of tear gas in Montreal.
I would describe it as a classic celebration riot. Professor Jerry M. Lewis
"It's not normal that when you're celebrating, there are people who start smashing things," Mr. Trudel lamented.
A festive street celebration in Montreal degenerated into looting and bottle-throwing after the Habs' victory against Pittsburgh on Wednesday night, ending in more than 40 arrests and soul-searching in a city that prides itself on peaceful street gatherings.
When it comes to hockey, however, experts say Montreal had many of the ingredients Wednesday night for a post-game blowout.
About 10 to 12 North American cities experience sport-related riots each year, and they share the same set of contributing factors, according to Jerry M. Lewis, a sociologist at Kent State University in Ohio and author of Sports Fan Violence in North America.
Fans strongly identify with their team, the fateful game comes late in the duel (it was Game 7 on Wednesday), and fans meet in a "natural urban gathering space." In Montreal, it was St. Catherine Street, Montreal's premier shopping street and a short walk from the Bell Centre, where 20,000 fans watched the out-of-town game on giant screens.
Also, the chances of rioting grow if it's been more than five years since a team's last victory. The Montreal Canadiens last won the Stanley Cup in 1993.
"I would describe it as a classic celebration riot," Prof. Lewis said of Montreal's upheaval. Participants are often young males, who identify so strongly with their team that "acts of violence become sporting acts."
Former Habs coach Jean Perron says fans didn't go on rampages when the team won the Stanley Cup routinely in the 1960s and 70s.
"When the Canadiens won regularly we didn't see this," said Mr. Perron, a television sports commentator. "Now fans are waiting and waiting and it's bursting. When there's impatience that's when it explodes."
Stir into the mix Montrealers' devotion to hockey.
"Hockey is more important than religion, it's more important than government," Mr. Perron said. He recalls that when he was coach from 1985 to 1988, nuns told him that they would pray for a Habs victory.
Hockey comes accompanied by periodic outbursts in Montreal. Riots followed Canadiens' Stanley Cup wins in 1986 and 1993. In 2008, cars were torched and stores looted after the Canadiens beat the Boston Bruins in the quarter-final playoff round.
The best-known disturbance came after legend Maurice Richard was suspended in 1955, setting off rioting that forced Mr. Richard to go on radio to appeal for calm.
Montreal police say they will review their strategy for the Habs' next hockey round, which begins Sunday, but they insist that they don't want to be killjoys for fans. In fact, most of Montreal was celebrating the Habs' victory peacefully. Police say an extraordinary 50,000 people partied joyfully downtown on Wednesday, until a rowdy crowd of 400 to 500 began to cause trouble.
"It was a very, very small minority of people that acted out," Chief Inspector Sylvain Lemay said in an interview. They do not appear to be hockey fans, either. "They came because they want to loot and take advantage of the crowd to be anonymous."
After the 2008 riot, police sharply increased their visibility on game nights in Montreal; hundreds of officers were present downtown Wednesday night on foot, horse, bicycle and motorcycle. Preceding the game, they visited shopkeepers and distributed papers warning merchants to "remove as many things as possible from your display window" when closing up, "to reduce the risk of break-ins and theft."
Aside from broken plate glass, the damage also wounded the self-image of a city that enjoys a good street party.
"We have a beautiful and elegant city that we're proud of," said Maskour Khalid, who spent much of the night in his souvenir shop, in the dark, while fans rampaged outside. "When you see this, it breaks your heart."