Sleep tight, my baby, mother's not going to burn you

My son learned how to read just after his 5th birthday. He reads everything he sees around. When we walked to the shop a while ago he was asking me questions like these:
Mother, What is a fucking cunt? (written on the wall)
Mother, do we buy Karjala? ( a beer brand)
Mother, when am I going to die?
He was reading the headlines of the afternoon-paper:
"... buried the girl killed by his brother"

Here are some headlines of the afternoon-paper posters he might have read recently:

Father was killed
Man lost in poker and tried to burn his family
This is the suspect of the cutting-up-murders
Brother searched his murdered sister
9-year old girl murdered - the whole village cried
Single-mother shot on her way to work
Police fired to kill
Father killed his children during the breakfast
Mother burned his children and herself

Two days ago he asked me a question while I was brushing his teeth.
Son: Are you really my mother?
Me: yes I am
Son: Okay then ( looking very doubtful)

What was he thinking?
Mother, are you going to kill me now?