Its very unfortunate when young children have to confront the fact that not everyone dies when they are very old or have been very ill for a long time
all three of my children had it stuffed right in their faces and minds when dh died in 2009
they were 2,4 and 9
all three of them went through a very unsettled, terrified I was going to die time
it really was torture for me not to be able to say only old people die
dh was killed in a carcrash, just turned out like a light
they kissed him goodbye in the morning and never saw him again
I just had to hold them and reassure them its rare for it to happen (I kow that not exactly true but you tell me what you would have said)
they spent a long time being visibly releived to see me after school and not wanting to be away from me
they got there eventually as will your child
I do think it is something every children realises at some point and is a developemental stage to realise that everyone could die at anytime
but with reassurance and plain talking they can get through it