Sometime in the near future, a caver gets lost in some caves in Arizona. He stumbles upon a city of what looks like glowing jellyfish underground. He soon realizes that these are sentient mushrooms, that use their roots for moving about. He witnesses one of these creatures catch a mouse and consume it using its roots/legs. The mushrooms scent him and start following him. They guide him to the surface by blocking off all the tunnels along his way that wouldn't lead out. The terrified caver reports his experiences, and brings some people back and shows them these creatures, and the story spreads from there.
Assume these creatures are two-three feet tall and docile to anything that is larger than them (and therefore not considered prey). These creatures mostly communicate by tapping their roots/legs on the ground. They also have a strong sense of smell.
Edit - These shroom-men (as you have dubbed them) move around on mycelium. Their "legs/roots" are the mycelium. The actual head part is for producing spores and storing food. It also is used for smelling and hearing. These creatures are sentient, and they are hunters. Their heads are hard, and they stand still, so when a cave creature comes by, thunk, they are smashed.
They probably bury the spores in certain areas, then protect the young shroom-children. The part of the menshrooms that looks like a jellyfish's legs is a kind of network of mycelium.
How would society in general react to this discovery? How would scientists react?