Before the fire erupted inside it, the thick black smoke blanketed it and the water cannons blasted through its windows, York Memorial Collegiate Institute had been preparing to celebrate a major milestone in its storied history.

The school, whose cornerstone was laid in Toronto's Eglinton Avenue W. and Keele Street area on May 6, 1929, had just marked its 90th anniversary when flames broke out there Monday.

Firefighters battled the blaze for some four hours before it was finally knocked down.

Then, in the early hours of Tuesday morning, flames broke out again, this time racing through the historic building and quickly escalating to a six-alarm fire, leaving much of the building gutted.

It was all too much for 2013 alumna Jaeybee Martinito, the valedictorian of her year, who looked on in horror as smoke billowed, memories of her time there replaying through her mind. The last time she set foot at the school was her graduation day.

Covered in symbolism

"That stage ... I spent a lot of my time on that stage," she said, recalling her time with the drama club and in dance class in the auditorium, believed to be one the worst-impacted areas.

"Oh my god."

Tuesday's fire was all too much for 2013 alumna Jaeybee Martinito, the valedictorian of her year, who looked in on horror as smoke billowed, memories of her time there replaying through her mind. (CBC)

But that wasn't the only reason Martinito was emotional.

Built in the wake of the First World War by the old township of York, York Memorial Collegiate Institute is covered in symbolism, its halls filled with history as a tribute to the young men in the community who gave their lives as soldiers.

"A lot of the students that went to this school actually fought in the war. So that's why I'm just thinking of everyone that's been part of this school," Martinito said.

It's a school named after those who sacrificed their lives for us, and the auditorium was a reflection of that. - Donna Drummond, York Memorial Collegiate Institute principal

Among those symbols: a mural by John Hall honouring those killed in the Second World War, stained glass windows commemorating the Battle of the Plains of Abraham in 1759 and Battle of Ypres in 1915.

And perhaps most visibly, a set of 11 steps leading to the front entrance, a representation of the 11th of November 1918, Armistice Day.

York Memorial Collegiate Institute's auditorium stage was beloved among students who spoke with CBC News. (Jim Djukarov/Facebook)

That a space so rich with history might be damaged by the flames had York Memorial principal Donna Drummond "devastated" and "heartbroken."

"It's a school named after those who sacrificed their lives for us, and the auditorium was a reflection of that," she said.

"The school has a long standing history in this area, in this community," she said. "It's a wonderful school, with wonderful staff and students."

'Memories in every inch of that school'

Jim Djurakov attended the school in the 1980s and says the ties that bound his generation of students together ran so deep that many of them remain friends even today.

Stained glass windows painted as a memorial to Canadian soldiers are one of the defining features of the school. (Jim Djukarov/Facebook)

"We had memories in every inch of that school," said Djurakov, who considers himself lucky to have taken so many photos of the interior before the flames broke out.

"When someone dies from York Memorial if they were in our generation, thousands show up because each person has touched another person's heart closely," he told CBC News.

Tuesday's fire marks a death too, he said. "We've lost a friend," he said, heartbroken at the loss.

For Toronto school board trustee Chris Tonks, the school holds personal significance too.

"I was absolutely devastated to see the depth of destruction," he said.

The school's cornerstone was laid in Toronto's Eglinton Avenue West and Keele Street area on May 6, 1929. It had just marked its 90th anniversary when flames broke out there Monday. (Jim Djurakov/Facebook)

"Many generations of my family have gone there, my father as well in addition to my grandfather. My grandfather actually attended in the first year the school was built," he said.

Tonks's father was a sports aficionado, he said, and still holds on to countless memories of his athletic successes at the school along with the friends he made there. He'd been looking forward to the reunion set for May 25, Tonks said.

Djukarov says that reunion has been cancelled.

No word yet on amount of damage

"We were going to have a big turnout," said Drummond, adding many were excited and looking forward to coming together for the school's anniversary. "It's a very sad day for all."

As of Tuesday evening, fire crews were still fighting the blaze, the scale of the damage difficult to pinpoint beyond what Toronto Fire Captain David Eckerman called "substantial."

York Memorial principal Donna Drummond teared up as she watched firefighters battle a six-alarm blaze at the school. 1:00

Some ceilings on the building's first floor had collapsed Tuesday, along with an exterior wall, though the conditions inside remain difficult to ascertain.

"I have no idea about damages yet," Fire Chief Matthew Pegg told reporters. Though "significant progress" has been made in knocking down the fire, heavy equipment is expected to be used Wednesday morning to help crews look deep inside the building for anything that may still be smouldering.

For now, generations of the school's alumni are coming together to raise funds to help with any rebuilding efforts.

For Toronto school board trustee Chris Tonks, the school holds personal significance too. (CBC)

Djurakov says there are also plans to raise funds to hold some version of a reunion on the school's back field, given the school itself will no longer be an option.

Kaitlin Wainwright, director of programming at Heritage Toronto, says she hopes to see a swift reaction from government, school board and provincial officials to help.

A collapsed exterior wall is photographed as firefighters battle the flames at York Memorial Collegiate Institute in Toronto. (Tijana Martin/The Canadian Press)

"What I'm going to be looking for in the next couple of days is some immediate response ... to making sure what's left of the building is restored and that essentially history is maintained," she said.

For his part, Tonks is trying to keep hopeful as well — that the school, an institution for the area, can continue on for another century.

"There is definitely a real tragedy in a personal sense here," Tonks said.

"But we will rebuild this school."