In 1995, 8,372 men and boys were killed by Bosnian Serb troops in the town of Srebrenica, Bosnia.
On Saturday afternoon, a white flower for each victim of the genocide was laid in front of the Notre-Dame Basilica.
Rusmar Rasic, one of the organizers of the Montreal tribute, said it's important to remember the lessons events like these teach us about humanity.
"Division between people can create situations where people will be killed," Rasic said.
Scars of the Bosnian War
During the Bosnian War (1992–1995), the United Nations declared Srebrenica a safe haven for civilians.
But on July 11, 1995, Serb troops overran the Muslim enclave. Some 15,000 men tried to flee through the woods toward government-held territory while others joined the town's women and children in seeking refuge at the base of the Dutch UN troops.
The outnumbered Dutch troops could only watch as Serb soldiers rounded up about 2,000 men for killing and later hunted down and killed another 6,000 men in the woods.
Mirela Hodzic lost her father in the genocide, at the age of seven.
She said she couldn't grasp the the magnitude of the situation at the time.
"Those are the first memories of my life, because the war started when I was four," she said. "For me it was a normal story, basically every-day killings."
The white flowers in front of the basilica will be distributed to passersby as a way of raising awareness about what happened 20 years ago.