Mako's mother asked him to get bananas. While passing the reef where he practices on his aim, he said, "When I finish getting my bananas, I'll be through with you." While on the island, he decided to make a basket to get the sweetest oranges in all of Bora Bora. By the time he was finished, it was already getting dark and he saw people lighting fires. When he got to the reef, he saw a dorsal fin that did not look like coral. He wanted to scream but he couldn't because he knew that the dorsal fin was Tupa's.
When Tupa charged, he tipped the canoe so Mako went to the other side to balance out the canoe but poor Afa fell in the water. He saw Tupa go after Afa when he was trying to swim to shore. In order to save/defend Afa, he threw a spear in one of Tupa's Eyes.
He then retrieved the spear and threw it at his other eye. Tupa laying on his back, not convincing Mako that he died, got speared in the shoulder and died.