Police say armed men broke into this southwest home on Riverdale Avenue S.W. late Thursday evening. (CBC)

Three masked men took six people hostage in a home in an upscale Calgary neighbourhood before robbing the homeowner's jewelry store, said police.

One man posed as a gas company worker and knocked on the door of the house in the 1200 block of Riverdale Avenue S.W. late Thursday evening, said police. Two accomplices joined him in breaking into the home.

Wearing masks and armed with handguns and a knife, they held hostage the homeowner, his 18-year-old son and four other men ranging in age from 18 to 20.

Two of the suspects took the homeowner to his jewelry business, Alberta Diamond Exchange, on 17th Avenue S.W., and robbed the store.

"They forced him to provide the offenders with access to his inventory. They stole a large amount of jewelry and tied up the victim before leaving," said Staff Sgt. Keith Cain.

He said the man was able to eventually free himself from the duct tape and call police.

The third suspect had remained at the home with the young men, who were also tied up with duct tape.

As a precaution, police took everyone inside the house into custody. (CBC)

At around 8:30 a.m. Friday morning, the police tactical team showed up and fired flash-bang grenades into the home. Inside, they found the young men, some still tied up. No one was hurt.

The incident did not appear to be related to drugs or gangs, according to police.

Police released descriptions Friday of the three suspects, all described as Caucasian:

• A man in his 20s, about 6-foot-5, with a slim build and wearing a black cotton hoodie, grey jeans, blue overalls and a full balaclava. He was armed with a silver-black handgun.
• A man about 6-feet tall, with a medium build and wearing blue jeans and a balaclava, and was armed with a baton and a hunting knife.
• A man of unknown age and height, with a stocky build and wearing sweat pants and white Nike runners. He was armed with a silver handgun.

'Pretty crazy start of the day'

Adam Lynch and Andy Buss were working on a construction project across the street from the house where the people were held hostage.

"We got here around 8:30 and we saw everybody kind of getting set up and then we heard five or six flash bombs, big bangs, kind of sound like gunshots. Then it went down fairly quick," said Lynch.

Members of the Calgary police tactical unit respond to the home invasion early Friday. (CBC)

"Pretty surprising — in a rich neighbourhood like this you don't expect to see a bunch of SWAT guys and cop cars rolling up to one of these houses."

"It was a pretty crazy start of the day," added Buss.

Lynch said lots of young people have been coming and going from the house over the past few days.

"Young people parked their cars, they're here for a little bit and then they leave again. We found that a little strange but figured maybe it was just a resident who had some friends."