The "call" as such wasn't made up -- apparently Tripp did make a call the company, and in a state of considerable emotional agitation.
Rather, it's the part about threatening to shoot the place up that was (according to the local Sheriff involved) basically made up (by the company, in its reporting to the press).
So basically an emotional phone call was recounted by a chain of people and blown out of proportion. Then the company felt the need to publicize it in order to get a little dirt on the shoes of the would be (and ultimately failed) whistleblower.
The sheriff sounds like a great and honest fellow, but the rest of this is just a mess. Of course, one employee running to the press with a "whistleblower" story that turns out to be misleading rubbish and doing billions of dollars in market damage isn't great. Responding to him this way isn't great.
What a mess.