Unless you are breaking the law, or he suspects you are, the cop has no lawful reason to detain you, seize your gun, demand your ID, detain you for any length of time, etc...
Why would there be a police report? The article said nothing of that. If the cops did not respond to a call that someone was on the trail armed, and someone got hurt. Would that be ok? That’s why we want to be able to carry in state and federal parks, because there are crazy people out there. How do the cops know if someone is or isn’t breaking the law, without investigating? Suppose the person was a felon and it was illegal for him to be armed or they were of middle eastern ethnicity? My info is available already.