Not a UAP story but It will show you how stories start and how credible and genuine observers may still be fooled. In the 70s, I was the First Officer of the Watch at a naval shore establishment in the UK. Around 2200, I was called by the guardroom to be told they thought the base might be under attack. When I got there, the duty staff said they were getting reports of an armoured vehicle firing at the base. That did not seem credible in darkest Hampshire, so I sent a team from the Duty Watch to the far end of the base, where the reports were coming from, to investigate and report back.
They confirmed there was a vehicle some distance outside the wire. They could not see it but they could hear it driving around across the fields and could see lights moving. More worryingly, they said they could hear short bursts of what sounded like heavy calibre gun fire. My first thought was a nearby Army camp might be having an exercise but a quick call eliminated that possibility. As whatever it was, was off base and there were no reports of damage or injuries, there was not much I could do - this was before the era of live-armed guards and the ROE at the time would have prevented me from arming the guard, let alone ordering them to shoot at an unidentified target.
Instead I rang the police, told them what has been seen and heard and where the vehicle was thought to be. Eventually, they called back to tell us it was a Land Rover full of slightly inebriated men out lamping for rabbits and the bursts of “heavy cal” were them blazing away with shotguns.
Now without that last sentence, the story would have been about credible military observers from a military base describing an attack, possibly by some form of “military” vehicle armed with heavy automatic weapons, which subsequently disappeared without trace and by now would a a “mystery”