This happened a few days ago. Two planes collided on approach to Centennial Airport in Greenwood Village.
Everyone walked away.
I have my own thoughts and ideas about what happened.
Here's a good thread on an aviation forum I follow, that has professional pilots, along with the latest information regarding the crash.
Mid Air in the US - PPRuNe Forums
The guy speaking in spanish in one of the videos is commenting on how the people are running. I'd be running too, if a plane is falling on me!