I am somewhat perplexed by your post.
You wrote, “Mr Horn should be fined for reckless discharge of a firearm inside city limits.”
What was reckless about using his shotgun as he so did was reckless?
Doesn’t prevention of a felony qualify as a lawful activity? If so, the discharge was legal, IMHO.
“Doesn’t prevention of a felony qualify as a lawful activity?”
(Texas)CODE OF CRIMINAL PROCEDURE
CHAPTER 14. ARREST WITHOUT WARRANT
Art. 14.01. [212] [259] [247] OFFENSE WITHIN VIEW. (a) A
peace officer or any other person, may, without a warrant, arrest an
offender when the offense is committed in his presence or within his
view, if the offense is one classed as a felony or as an offense
against the public peace.
http://tlo2.tlc.state.tx.us/statutes/cr.toc.htm