There seems to be a mish-mosh of reports on this incident. Here's an early one which does not mention a rifle at all.
https://www.click2houston.com/news/1-dead-2-men-hospitalized-after-shooting-in-north-houstonApparently, the thrust of the ammoland article is to emphasize the need for the most effective defense weaponry, suggesting that full auto and "high" capacity magazines add to this effectiveness.
As such, author Dean Weingarten did not go into details on the background. I found a couple of other links by searching on the address involved. Apparently, it is or was an <ahem> "active" area, since another story reports on a storekeeper on that street defending his property with a firearm.
So while there's a legitimate question as to why the AR owner was out there fully armed at 2:15 AM, that was apart from what Weingarten was trying to convey in the OP's link.
In other words, some Who, What, Why, When, and Where answers were omitted by Weingarten in order to make another point. However, I personally am not willing to dig out these additional WWWWW details beyond just search-engining the address.
Terry