what is mother?

In Hyogo, a mother fell down the platform with her two children and all of them dead instantly. Children are 3 and 1 age. Her husband said he hasn't light idea about why she decided suicide, so police suppose it is double suicide. By the way, why she fell down with her children? Children has their future and their life is just began. Mother is who support her child and watch their growth, isn't it? What happen for her? I'm going to watch carefully this news.