Answer:
They believed that the gun was protecting the city, but the gun was protecting a tomb with artifacts from an ancient civilization.
Step-by-step explanation:
"The gun" was written by Philip K. D*ck and tells the story of a group of astronauts who were hit by a gun that fired at anyone who passed over the city where it was established. Although they believed that the weapon was intended to protect the city, they were mistaken, because after much research, they discovered that the weapon was protecting a tomb that contained artifacts and documents from an ancient civilization.