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Due to challenges posed by information processing in Autism, death & bereavement can pose special challenges in these children
I would like to give a few tips and then direct you to a couple of excellent web resources that should help
When dealing with death and bereavement in an autistic child, the following thins help...
Since autistic children tend to respond better to clear & simple language and visual clues, it may be helpful to use some of the below mentioned strategies
"For example, if you describe death as "like going to sleep" you may make the individual terrified of going to sleep at night. Something simple such as "sometimes people's bodies become worn out" may be appropriate. If they want to know what this means, or how it will affect their lives, you could say that they "will not see Grandma again".
Sometimes using the example of a bird or an insect may help to understand the concept of death
Finally, for many kids of this age, fear of death can be an important issue, and here are are a few things that can assist,
Perhaps the kindest thing parents can do when dealing with a child’s fears is to admit their own childhood fears, especially if the parent had similar fears when he was a child. Then parent can indicate that he understands just how devastating such fears can be and that he stands ready to reassure and comfort whenever the child feels a need.
I would recommend using some of the above mentioned techniques, and getting back for any clarifications
References & further reading