My instinct here, which is worth exactly what you paid for it, is that something is not quite right with the account. (The Guardian cross-posted this also)

The piece describes the searchers as not even opening the door of their 20 year-old son’s bedroom (because he was asleep inside at the time). That sounds odd to me, given how many shootings there have been by unhinged young men who came off the rails so horribly without the parents either knowing about it or knowing what to do about it.

It all could have gone down as described, but my instinct is waving a little red flag in the corner of my mind.
If it did indeed happen this way, and their internet searches are what triggered the visit, then that’s disturbing and quite contrary to the authorities’ recent denials.