On the topic of former marines involved in shootings, about 3 months ago an ex-marine moved from somewhere in California to Houston because it is easier to buy guns in Texas. The day after he arrived he was in the street shooting at people and a helicopter (which he managed to hit 5 times, so a pretty good marksman). He was there apparently to kill non-Christians. The whole situation is quite worrying.
A bar I used to visit in Houston had a customer who would wear a t-shirt that read, “US Marine, I kill people so you don’t have to”. It wasn’t a rough, or serviceman’s bar. They, especially in Texas seem to have a different view about killing people than than the folks in other countries. They practically worship their military people which I think gives them a different view on killing ‘the enemy’ than in countries where this isn’t the case. They also have a very different world view that from outside could appear to be paranoid and brainwashed. Oh, and a lot of people have served in the military.
Every one knows it is easy to buy a gun in Texas, but it really is very easy. I went to a big-box sport shop to buy a beach shelter. While there the guy told me that Colt AR15s were on sale. $400 including a scope. That was about a year ago , so less than £250.
From by brief experience of the place, it is a very troubled country whose citizens believe is the best place on earth.