How does nag dies in the Rikki-tikki-tavi story?

Nag dies in Rikki Tikki Tavi when Rikki Tikki Tavi was fighting him. Right when Rikki Tikki Tavi was on top of him he bit him and he got weak. The snake was still alive so then the big englishman came out and shot Nag. Then he dies.

Hope this answered your question(: