The ironic thing is that this would probably be the very last thing their mother would have wanted her three daughters to do.
It is interesting they were all living together, they were roughly all in their early to mid thirties. They have different surnames from the father, and each other. It was 16 years since their mother’s death. So they would have been roughly 20, 16, and 15 when that happened.
They must have been quite miserable, and maybe life had been difficult in the 16 years since their mother died. Maybe beforehand too, as their mother ended her own life. I suppose nobody will ever know the full story now of what led them to this.