For Volta, suppressing his humanity enough to glean a room full of children is too much for him to live with. Volta is only around 20 years old, so it's telling that killing children at this age is enough to make Volta want to die—according to Curie, most scythes don't self-glean until they're more than a 100 years old. This also represents a turning point for Rowan, as he sees right in front of him the lengths that Goddard will go to spread fear and corrupt his disciples.