The shooter who rampaged through Canada's parliament took a video of himself just before the attack and was inspired by ideological and political motives, police say.
However, his mother says Michael Zehaf-Bibeau, who was shot dead by police in the parliament in Ottawa after killing a soldier on Wednesday, was mentally ill and wanted to die.
But labelling it "a terrorist attack", Royal Canadian Mounted Police (RCMP) Commissioner Bob Paulson said that the 32-year-old "was driven by ideological and political motives".
Zehaf-Bibeau had prepared a video recording of himself just prior to conducting the attack.
In her letter to Postmedia News, published in Sunday's edition of the National Post, the killer's mother Susan Bibeau said her estranged son had wanted to travel to Saudi Arabia to study Islam and the Koran, not Syria to join militant fighters - as stated before by police.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
But when his passport application was repeatedly denied, Zehaf-Bibeau felt trapped, "unable to stay in the life he was in, unable to move on to the next one he wanted to go to", his mother wrote.
"He was mad and felt trapped so the only way out was death."
She stressed that, while "horrified" by her son's actions, he had suffered from deep psychological problems.
Zehaf-Bibeau killed a soldier and attempted to storm parliament before the assembly's sergeant-at-arms shot him dead.
The attack - the second in a week targeting Canadian military personnel on home soil - came as Canadian jets were to join the US-led bombing campaign against Islamist militants in Iraq.
Police were investigating Zehaf-Bibeau's interactions with "numerous individuals" in the days leading up to the attack, Paulson said, adding that the young Canadian had saved up a considerable amount of money from working in oil fields.
