Have you talked to your neighbor about this? Not the one with the kids that raid your pantry; the one with the guns.
If not, why not? After all, if you think you have a right to know about his guns, he has the right to know he has a neighbor with mental health issues who is prone to parade them on social media.
You might want to seek professional help with your issues. There are at least 80 million gun owners in the U.S. There are 16.3 million Americans with concealed-carry licenses. There are a dozen states that do not require a permit to carry a concealed handgun. There are also hundreds of thousands of law enforcement officers, most of whom are required to have a gun on their person even when they are in plain clothes or off duty. So on any given day, you may well be in close proximity to someone that is carrying a loaded firearm — and you won’t even know it.