The crux of this is they don't like anyone owning guns. They seized the guns even though they didn't charge him. It seems to me if they had a complaint that was legally actionable, the warrant (if there even was on) would have stipulated such. The article implies that he wasn't 'allowed' to own guns because of "mental health issues" but doesn't say what the 'issues' were/are.
NEVER tell the government or even local authorities what you own let the incompetent mother effers figure that out on their own, NEVER talk about or brag to your neighbors, either.
And never keep them all in one place.