"When something like this comes up, we take it very seriously," Krob said.
The video surfaced just days before New Year’s Eve and included threats of a terrorist attack. In the video, Denver’s skyline makes up a very small part of the video that included other cities around the world, Krob said.
"We met with the mayor. We met with the chief of police,” he said.
A decision was made to go ahead with the city’s downtown celebration, Denver7 Investigates previously reported.
"We called in FBI resources from the field office, folks that weren't planning to work that night. We were embedded with the Denver Police Department for New Year's Eve," he said.
No attack occurred.
Krob says the type of terrorist he is most concerned about is homegrown violent extremists, or so-called "lone wolves."
"Those people are really the people that concern us because we may not find out about those folks. In some cases, they may act out before we have a chance to stop them," he said. "We're seeing what we call soft targets start to be the area of focus for these actors who can't otherwise go join the fight somewhere, but want to act out domestically and do something."
Krob, who is privy to classified material not available to the general public, suggests members of the public not be paralyzed by fear.