Awwww. I am SO sorry. That's such a trauma for youngsters, especially the first time they watch a hatch. That "Circle of Life," thing is a tough lesson, even for grown-ups! My matter-of-fact, dairy farming sister always told my children, "Sometimes, when you have livestock, you have dead-stock." They're nearly grown, now, but they'll still quote their aunt.They are all dead.
New chicks should help ... post pics, please?