Suicide and Killing

A 17 year old Japanese girl in Yokohama jumped of a tall building to take her own life. This would not be much of a story, if it were not for the fact that she hit another human down below. The other human, a 32 years old woman, also died. 

Why do some humans take their own lives? Dogs never commit suicide. I cannot understand why you want to take your own life. There are so many joys in life, like meatballs. I would never need to take my own life