Dr. Neil McGee is used to saving lives in the emergency room at the Queensway Carleton Hospital. But on Sunday he found himself stepping in at the finish line at Ottawa Race Weekend.

"I happened to be standing beside a couple of paramedics and they were told there was someone who had collapsed and was getting CPR," said Dr. McGee.

25-year-old Chi-Son Do from Montreal collapsed during the half-marathon on Sunday and had a heart attack.

Dr. McGee said he ran to where Do collapsed, just 200 metres from the finish line.

"Coincidentally one of the people who was doing CPR was a doctor…and he happened to be a cardiologist in training from Halifax."

"The runner had collapsed. His knees just buckled out from under him and he fell face first into the pavement," said Trevor Johnston, a photographer who arrived minutes after Do collapsed.

Johnston said Do's eyes rolled back and he thought he was dead.

"It was terribly frightening to see…not something I ever hope to see again."

Minutes after Dr. McGee and another doctor administered CPR, Do started moving again.

Dr. McGee said his message is that anyone can save a life.

"The man survived because he got early CPR," he said. "By the time the ambulance arrived actually he was even talking."

Paramedics said they took 12 people to hospital over the weekend, including a man in his 40s who collapsed near the 10 K finish line on Saturday and was taken to hospital in critical condition.

With a report from CTV Ottawa's Stefan Keyes