AURORA, Colo. (KDVR) — An HVAC system collapsed and injured six people at the Gaylord Rockies Resort & Convention Center Saturday in Colorado.

Of the six people who were injured, two had life-threatening injuries and four had non-life-threatening injuries.

According to the Aurora Fire Department, the collapse happened around 9:50 a.m.

Jamie Olson, who took a video showing the collapse’s aftermath, told Nexstar’s KDVR her son had just gotten out of the hot tub when the system collapsed directly on top of it and the rest of the pool.

“We were right on the outside of the hot tub, and just kind of heard a big groan, and we looked up,” she said, “and it was just like a domino effect. One side collapsed, and then it caused the other side to collapse.”

Olson said a black sludge poured out the ceiling, and her husband saw two kids covered in it.

“I think that’s the scariest part was that there were kids down there that couldn’t find their parents,” she said. “And we would’ve sent our kids down there, no problem.”

Olson said the immediate response from everyone, from guests to staff, was “incredible.”

“I think that if you could respond to such an unprecedented event that nobody is trained for,” she said. “They don’t train lifeguards for that — ‘What if the HVAC system collapses in the pool?’ — I think that everyone did a pretty good job.”

She said that even though people were rattled, everyone did the best they could during the situation.

“Everybody jumped in to help,” she said.

According to the fire department, an investigation into the collapse will be up to the hotel to conduct.

The pool was closed for repairs Sunday, but fire crews said the rest of the hotel was safe for guests.