Were they positive he had a "Regiment" waiting for him? Was he still in the U.S. Military?
From what I can see, is that he was a man who moved to Texas to gather and sell horses to the U.S. Army, wouldn't swear allegiance to the Confederacy, sells his Texas belongings at a big loss, leaves voluntarily according to a law (that leaves me to wonder if "Alien/Enemy was actually defined), and is rounded up on trumped up charges and arrested...don't look like he was going to be tried anytime soon?
"much less conspicuous men than Father were mysteriously killed for their sentiments..." the diarist writes...what of those folk she speaks of? I know of some that WERE TAUGHT Confederate laws/values at the end of a rope, or gun barrel.
We need to remind ourselves that BOTH sides behaved badly before/during the war, and many were not safe from tyranny on both sides of the border.
The door swung both ways.