Who is Luis Cruz from Tangerine and what is their importance?

Luis Cruz is the older brother of Theresa and Tino, Luis has a limp from falling out of a tree at a young age. His family is involved in the citrus business and Luis has engineered a new species of tangerine. Luis goes to the Lake Windsor High School football field to confront Erik after Erik hits Tino. But at the school, Arthur hits Luis in the head with a blackjack, and a few days later Luis dies of an aneurysm. Paul greatly admires Luis and that admiration prompts him to tell the police what he saw and heard during the attack.