Actually, the father did not interrupt illegal activity. They were fully clothed and not engaging in relations. The boy was hiding under the bed, for goodness sakes. Again, the boy was invited in by the daughter, so no reasonable person is going to claim he was an intruder or a trespasser.
So if it the father's castle and the father does not like any of his kids' friends, by your theory, the father can shoot anyone he doesn't like that is in house. You are trying so hard to justify murder that you have become ridiculous, if not downright immoral in your reasoning.
Texas Penal Code Title 5 Chapter 21.11 says exactly what I stated earlier. It is a crime for a 17 yr old to engage in a sexual relationship with a 16 yr old. Subsection (b)1 states that less than 3 yrs age difference is an affirmative defense to prosecution.
That doesnt make it legal.
That’s what I said.
If you don’t want to risk a father’s wrath and all that entails, then don’t screw his daughter under his roof. The situation is unfortunate. We all did stupid things when we were young, sometimes things that should have gotten us dead or in deep trouble. In this case, the kid didn’t scrape by like we did. His fate caught up with him. Tragic: yes. Murder? I’m afraid it’s you who’ve become ridiculous.