Complex sentence: He is struck over the head twice with a canister, the first time causing him to malfunction and the second decapitating him; and he is then, when even that fails to kill him, electrocuted with a cattle prod.
Split into simpler sentences: He is struck over the head twice with a canister, the first time causing him to malfunction and the second decapitating him. When even that fails to kill him, he's electrocuted with a cattle prod.