The Denver Nuggets championship parade just took a somber turn ... a police officer was rushed to the hospital with serious injuries after being struck by a firetruck that was participating in the ceremonies.
According to the Denver Police Dept. ... the incident happened just minutes ago while the truck was driving along the parade route in the Mile High City.
You can see in video from the scene, Nuggets superstars Nikola Jokic and Jamal Murray -- as well as the Larry O'Brien trophy -- were on the vehicle when the accident occurred.