Who hits Luis with a blackjack in Tangerine?

The narrator of Tangerine, Paul Fisher, has an older brother called Erik. Erik's the blue-eyed high-school football star who can do wrong in his parents' eyes. But he always seems to go out of his way to make life difficult for his kid brother. For instance, when Paul's hanging out with his friend Tino one day, Erik punches Tino in the face, knocking him unconscious. When he hears about this, Tino's cousin Luis goes looking for Erik to confront him. He arrives at the football field, ready for a showdown. But Erik's not prepared to waste his valuable time arguing with Luis, so he instructs his friend, the thuggish Arthur Bauer, to take care of things. Arthur does as he is bid and whacks Luis across the side of his head with a blackjack. The attack doesn't kill Luis straight away, but he dies from a brain aneurysm just over a week later.