First of all, Felina was a dancing saloon girl; her job was to dance for the cowboys, and get em to buy drinks. So being jealous of that behavior is like getting jealous of your chef wife cooking dinner for other guys.
Second, our narrator started the fight by “challenging” the wild young cowboy. If you were having a good time at a bar and some armed whacko stepped to you, wouldn’t you reach for your gun? I would. That’s second degree murder committed by our psycho stalker jealous narrator, and an innocent man trying to defend himself.
Third, the police didn’t kill our narrator. Five mounted cowboys to his right, off to his left were a dozen or more. Not cops, sheriff, marshals. Cowboys. These are the dead guy’s buddies, or else irate townsmen who think our narrator is psycho.
And what does our narrator do? “Shouting and shooting and shooting, I can’t let them catch me; I have to make it to Rosa’s back door.” Our narrator is doing all those verbs: shouting, shooting, riding. This sonofabitch starts another gunfight, but some concerned citizens with rifles end his reign of terror.
The narrator of Marty Robbins’ masterpiece was a piece of shit. He got exactly what he deserved.
Great song, though!