Jory (1973) Robby Benson.

Jory's father is a lawyer who plays classical music on a saloon's out-of-tune piano. He gets himself killed by continuing to antagonize a much larger man even after he pulls a knife on him.

Jory (Robby Benson), watches the murder through the window.

Now an orphan, Jory unwisely confronts the killer.

"Why did you kill my father?"

It seems like a skinny teen killing a big violent drunk with a rock would be an obvious case of self defense, but Jory flees the area by joining men driving a herd of horses to Texas. 

This happens in the first ten minutes so I'm not giving anything away.

Coming of age stories always have a Young Adult feel to them. That was the case here even though the boy kills people.  Later, he sees a naked girl swimming.

A cowboy introduces Jory to shooting which turns out to be a natural ability rather than an acquired skill.

Robby Benson must have been sixteen or seventeen playing a 15-year-old. His first major role. He spoke very softly and he must have cried a few times, but it was the most ruggedly masculine role any young boy could ever hope to play.

Available on YouTube.

I never heard the name "Jory" before. I googled it and looked at a website for baby names. It's unisex and means "farmer". And, in 1973, when this movie was released, it had a spike in popularity.