After reading a while, I wanted to touch on a couple things I've read and give my 2 cents.
Re: Children alone in Walmart.
Well known fact in retail that mexicans, blacks, and white trash tell their spawn to go play in the toy section while they shop a quarter mile away. The assumption is, it's free daycare.
Re: "It's Texas. Why didn't someone pull a concealed and blast away?
Multiple reasons why not. Mainly, this is a border town of mostly mexicans (legal or illegal) and most likely overly liberal views of its citizens, (guns are bad). They couldn't/wouldn't carry a weapon. Not a lot of good old boys down there that would be the ones carrying.
Secondly, if you are carrying, most likely smaller caliber, and have done any shooting, you would most likely know you were out gunned, and go into self defense mode, hiding and protecting yourself and family if it was necessary.