McDohl quest: Instant death on Worm?

[KFCrispy]

Konami is streaming a playthrough of Suikoden II and Yuichi (the Konami player) tried Hell on the Worm in the McDohl quest (saving Ko). Strangely it seemed to work, because immediately after the spell, the Worm changed into the Moth(ra).

Our Bestiary says the Worm (2nd Fight) is invulnerable to instant death, so I'm just wondering what happened. I know the battle is semi-scripted, so was it simply the Worm's turn to act after Hell and the action was to change to the Moth?

[sticky-runes]

I think the monster goes still immediately after losing all HP, and then it will transform in the next round. So if the monster was not doing it's wriggly animation at the time the instant death spell was cast, then likely a different character struck the finishing blow, and it became the moth in the next round. I guess.

[KFCrispy]

what i witnessed was it transformed immediately following the spell.