Assessing self-defense

Dear PAO,

At a barangay fiesta, our neighbor ran amuck and attacked my uncle, a barangay tanod on duty, with a bolo. A bystander and I intervened to help, but the attacker turned to us. In the chaos, I fell to the ground, and the attacker severely wounded me. I managed to struggle with him, but my uncle, who was already injured, ultimately dealt a fatal blow to the attacker, which caused the latter's instantaneous death. My uncle was charged with homicide. Allegedly, his action was unreasonable because he inflicted a single mortal wound, which caused the demise of the attacker. Is my uncle liable for homicide?