Kakashi and Zabuza resume their fight. Due to his Sharingan, Kakashi is able to take the upper hand and he defeats Zabuza by copying his own attack. Before Kakashi can finish him, a masked Kirigakure hunter-nin apparently kills Zabuza and leaves with him. Kakashi then collapses from fatigue. Source: Wikipedia Naruto Episode 9 – Kakashi: Full Article