I heard this by the Har Nof tragedy, and I heard it again now. (The person who said it over mentioned a source – I pretty certain it was in Yeshaya, and also something R’ Moshe Feinstein said regarding a tragic accident in his time.)
Every time Hashem takes people from us in an unnatural way it’s a korban for klal Yisrael – how? Klal Yisrael are wonderful but at different times we have different weaknesses. When one particular weakness becomes a kitrug against us, we need a zechus to save us. Hashem chooses people who do NOT have those weaknesses – people that are actually strong in those areas and He takes them as karbanos. When that person’s Neshama leaves this world, their maasim tovim protect us more than while they were alive.
So perhaps something we can do is try to find out about what kind of children the Sassoon children were. What did they excel in?
And we can take inspiration and a lesson from that.