4 year old shoots babysitter

A 4 year old child shot his babysitter for accidentally stepping on his foot. According to police the child got very upset that he stepped on his foot, and ran to get the shotgun in the other room and shot Nathan Beavers, 18 years old. Nathan was sent to the hospital. But the 4 year old was not the only child there, there was several other children there. There where other teens there but him and an other boy where hurt by pellet wounds



Now I'm wondering why they have a gun, in the house, not only a gun, but a shotgun at that. Where kids can reach it and hurt themselves or others. the child was not convicted.
What are your thoughts?