An emotional Glen Gieschen stood in court and told the judge he takes responsibility for his "irresponsible" actions in January 2014.
Police recovered firearms, body armour, possible bomb-making materials, schematics of a downtown Calgary skyscraper and a plan to attack the seventh-floor federal offices during Gieschen's arrest in January 2014.
"It was wrong for me to have that plan," he said at the end of sentencing submissions.
"My thoughts go out to the people that have been harmed and that being, first and foremost, the staff, their colleagues, their families, their kids. I can only imagine the horror and fear they must have felt when they saw that in the papers. That would be a horrible thing to come to work thinking some of the people that you're trying to help, that have served this country, would want to do a harm to you."
A date for sentencing will be set Thursday.
Crown prosecutor Doug Simpson told the hearing that Gieschen still poses a danger to the public and should serve between four and six years.
He argued that although Gieschen claims he planned to commit suicide, the large amount of firearms he was found with indicates the plan was no fantasy.
"The fact there was the potential for serious bodily harm or death to have occurred to a number of innocent people is sufficiently evident," Simpson said.
He noted Gieschen visited the Veterans Affairs building the day of his arrest and he was just steps away from carrying out his plan.
"All that stood between that attack occurring or not occurring was Mr. Gieschen," he said.
Court has been told that Gieschen, 45, had a beef with the military over coverage for multiple sclerosis he believed was caused by a flu shot he received while in the military.
He claimed he was the head of military intelligence, but court heard he was a 2nd lieutenant when he was put on long-term disability in 2011.
The defence argued he should serve a minimum three-year sentence in a federal prison so he can get psychological help.
Gieschen was arrested after his wife called police because she was concerned that he might be suicidal. He was taken to hospital for treatment under the Mental Health Act.
When he was arrested at his parent's rural home west of Calgary, he was dressed in camouflage pants and was sleeping with a duffel bag near his head.
The bag contained a .40-calibre semi-automatic handgun that was loaded with a full magazine. Police also recovered a .308-calibre rifle, a ballistic range-finder scope for shooting long distances, a laser sight for shooting at close range, night-vision binoculars and 1,000 rounds of ammunition.
There were also jugs filled with chemicals, empty suitcases with metal linings, 16 black sticks with a protruding fuse, carpenter nails, threaded pipes and six tubes of camouflage face paint.
Police also recovered black gun powder, 16 canisters of bear spray, 25 smoke grenades and a gas mask.
Judge Sean Dunnigan noted that there are very few cases that he could reference in deciding on a sentence.
"The world doesn't see Timothy McVeighs very often," he said.
McVeigh detonated a truck bomb in front of the Alfred P. Murrah Federal Building in Oklahoma City on April 19, 1995. The attack killed 168 people and injured more than 600.
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