WATCH: Heavily armed SWAT unit bursts through gamer's door after prank call

A dangerous prank prompted a SWAT raid on a Colorado gamer Wednesday, when an anonymous caller told police he had shot multiple people at an office building.

Heavily armed police burst through the door of an office in Littleton, where gamer Jordan Mathewson was playing Counter-Strike, reported KMGH-TV.

Mathewson -- who calls himself "Koostra" online -- is part of a gamers group called The Creatures, who livestream video of themselves playing against one another online, and he recorded the entire incident.

In video posted on YouTube, the gamer suspects he may be the victim of a “swatting” prank because he can hear officers clearing the building outside the office door.

“There’s a somewhat, not really common, prank that happens,” said Daniel Gidlow, another member of The Creatures. “While we’re live streaming to thousands of people, somebody calls the cops.”

Mathewson removes his headphones just as police enter with their guns drawn and order him to the ground.

At least five officers surround Mathewson, who is handcuffed and then questioned.

One of the officers demands to know what Mathewson, who can be seen on the video chuckling as he realizes he has been pranked, finds so funny, but the gamer insists he finds nothing humorous about the situation.

Mathewson tells police during questioning that he has some fake prop guns at the office, and police said their examination of those phony weapons slowed their search of the building.

The officers eventually realize they have been taken in by a hoax, and they let Mathewson go.

Police initially detained several gamers for questioning, but they did not make any arrests and said the other gamers cooperated with the investigation.

A Twitter user who goes by the name @ScrewPain is claiming credit for the prank, which has been perpetrated against other gamers across the country and celebrities such as Justin Bieber.

“This is not an online game,” said Littleton Police Chief Doug Stephens. “We have real guns, real bullets -- and there is a potential there for some tragedy.”

No injuries were reported, but others who work in the office building said the experience was frightening.

“It was a bit intimidating,” said Jeff Barela, who works next door. “The police came in and said, ‘Hands up, we need to see them.’ They had guns drawn and they escorted us out of the building.”

Several neighboring schools were also placed on lockdown while police searched the area.

Watch video from the SWAT raid posted online by MaxConsole: