Betrayal at House on the Hill, Haunt 42: can Explorers be used if they are killed by an event? (spoiler)

Question

For Haunt 42, Comes The Hero,

the Traitor needs a 'sacrifice' to open a gate to Hell, consisting of an Explorer

If an Explorer is killed by an event, can they be used, or does the Traitor have to be responsible for the kill?

Answer 1

The Traitor's Tome says of the Traitor,

You must sacrifice (kill) one of the heroes using a weapon ...

which excludes a death due to an event.