"A very sharp, observant sheriff noted a suspicious package or device going through the X-ray and took the person into custody right away," said police spokesman Kevin Brookwell.
"The response was quick and the action we took was to ensure the safety of everyone involved. It just takes time when you're dealing with something like this."
Little was known about the individual who arrived at the courthouse around 9 a.m., said Brookwell, although the man was co-operating with police.
Hours later the bomb containment unit used its robot to remove the device.
"It's been put into our safe vessel. It's going to be taken to an undisclosed location here in Calgary, where they'll have a closer look at it using some of the other equipment they have ... in a more safe environment," Brookwell said.
"At some point they will be looking to either disrupt it or render it safe, so they can see exactly what they have, but that could take some time."
The downtown area was shut down for six hours before officers began taking down yellow police tape. All court proceedings and trials were cancelled for the day. Some staff were sent home early.
The courthouse itself was still a "crime scene," said Brookwell, who added the suspect had left behind some belongings that needed to be checked out
Officers were also searching a vehicle in a northeast Calgary parking lot, Brookwell added.
He said police don't believe that anyone was in danger, but felt it was important to be cautious.
"I would rather be criticized for a massive overreaction," he said.
"In the end ... I'd rather say we did what we thought was right at the time and it ended up being nothing, rather than something happening and being asked why didn't you take the necessary precautions?"
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