"I'm here as a fellow human being," Horwath said as she attended the Toronto Emergency Services memorial dressed in black.
"Yes we are in the middle of a very rigorous election campaign but there are some times when you have to step back and say the world is a bigger place than just Ontario politics."
The ceremony was the lone event on Horwath's schedule Sunday while Progressive Conservative Leader Tim Hudak and Liberal Premier Dalton McGuinty had slightly busier agendas that also included in 9-11 memorials.
Sunday marked a decade since terrorists crashed fuel-engorged jetliners into New York's World Trade Centre buildings, the Pentagon and a field in Pennsylvania. Nearly 3,000 people were killed, including 24 Canadians.
Speaking to reporters at the mid-morning event, Horwath extended her sympathies to families who lost loved ones in the events that stunned the world.
She also thanked all the first responders who stepped in to help amidst the chaos that was the aftermath of the attacks. A number of Canadians were among those who rushed to New York to lend a hand after 9-11.
"I'm here really just as a person to say how much I have sympathy for the loss and also thanks for those who did so much great work at their own personal risk on that day and the days following," she said.
As she mingled with the public and took in a list of all the emergency workers killed on Sept. 11, 2001, Horwath said the tragedy, terrible as it was, was also an opportunity to focus on understanding cultures and faiths around the world.
The NDP leader was a guest at the memorial held in Toronto's Nathan Phillips Square which included a march-past by Toronto police, fire and EMS honour guard units.
The event also featured speeches from the heads of Toronto's emergency services departments and an address by U.S. Consul General Kevin Johnson.
Johnson said the day was one to mourn "incredible losses" but also one to commemorate the heroism of those who responded to the attacks.
"We can never forget that service that is ongoing and as well as that service of those who paid the ultimate price 10 years ago," he said.
McGuinty met with members of the Oakville fire department at a pancake breakfast in the morning before heading to another memorial event in London, Ont.
The London ceremony honoured the 343 firefighters who were killed on 9-11 when the twin towers collapsed, as well as remembering the 21 London firefighters who have died in the line of duty since 1855.
"It's hard to believe it's been 10 years," McGuinty said to the hundreds gathered for the memorial. "We all remember where we were and what we were doing that day. We all remember how the day unfolded, hour by hour and image by image. The sight of those buildings collapsing and the thought of those people trapped inside is something that will live with us forever."
McGuinty, who also helped unveil a new monument to the fallen London firefighters, said first responders and others made so many sacrifices that day.
Hudak, joined by his wife Deb Hutton and three-year-old daughter Miller, started his day by placing a wreath at the U.S. consulate in Toronto.
"Very sadly, of course, 24 Canadians were killed in 9-11," Hudak said at a later event in Hamilton. "Our thoughts and prayers are with all those families. And being here in particularly in the Hamilton-Niagara area where we have a very special relationship with our friends across the border, our thoughts and prayers are with the American families on this tragic day."