Canadians on Thursday mourned the loss of Cpl. Nathan Cirillo, the army reservist who was shot dead as he stood guard before the country's Tomb of the Unknown soldier.

Flags were flown at half-mast to honor Cirillo, a 24-year-old a reservist from Hamilton, Ontario, whose shooting on Wednesday began an attack that ended with a lone gunman storming into Parliament and opening fire before being shot dead himself.

Cirillo was a life-long military enthusiast who joined the cadets at age 13 and was training to become a full-time soldier, according to Hamilton mayor Bob Bratina.

"When you're a soldier you understand that when you go into harm's way that there's always the possibility that the worst could happen, but who would ever think of it standing in ceremony," Bratina said, adding that Cirillo had only been assigned to the post in the last day or so.

Military representatives were meeting with the family who declined to talk with reporters.

Friends remembered Cirillo as a loving father to his six-year-old son, a gregarious outdoor enthusiast and fitness buff, always eager to help friends.

"He knew what he liked and what he wanted, and being a solider was one of his main goals. He loved watching war movies, and his son, he absolutely loved his son and tried his best to be a loving, fun parent," said Ashley Moerschfelder, 19. Cirillo was separated from his son's mother, said another friend.

Danielle Townsend, 24, said Cirillo was the most compassionate person she had ever met.

"He was the type of guy that would go out of his way to make someone smile if they were having a bad day. He was all about family, friends and loyalty," said Townsend, adding that he was considered the class clown when he attended Sherwood Secondary School in Hamilton.

Cirillo became a personal trainer after high school and also worked as a bouncer at a bar in downtown Hamilton.

Ontario New Democratic Party Leader Andrea Horwath, who represents Hamilton, expressed her condolences, saying Cirillo served bravely with the city's Argyll and Sutherland Highlanders — the 91st Canadian Highlanders.

At his home armory, soldiers watched through the locked gates Wednesday evening as people added flowers and stuffed animals to a growing memorial for their slain comrade.