I don't understand

I received some very sad news. Devastating news. And I can't even begin to understand. My friend's sister died by her own hand. She hung herself. And now I sit here staring at those three words staring back at me on the screen. I am shocked, sad, and, dare I admit, slightly angry all rolled up in one. I did not, of course, know everything about her life. But, does anyone really know everything about someone? I did not know if there was something causing excrutiating pain or unbearable depression, or some other burden that she felt could not be resolved. What could be so bad to make a person feel so desperate that they take their own life -- and leave a husband and two small children behind?

My friend, understandably, is beside herself. She feels personally responsible, as if her sistersly bond should have detected it and been able to stop it. I am unable to console her, nor is anyone else. Her grief is heavy, as she looks into two pair of wondering eyes. They don't understand where their mother is. They don't understand the weeping, the overwhelming sadness in the house. My friend wonders how they are going to explain to those two precious children that their mother is gone. She wonders how they are going to grow up without their mother's love and support and encouragement. She's feeling such terrible guilt.

No, I don't understand.