Thank you for asking me.
Being a Buddhist doesn't mean that the person is well versed with the Buddha's teachings, especially for an 8 year old child. Assuming this child has nothing to do with the person's death, you can try narrate the Buddhist story below which reminds us of the inevitability of death. But for an 8 year old child it may be difficult to get the message across. Don't worry too much over the present scenario. Given time it will pass, and all will be normal again! For the present, just try to avoid doing or saying anything that reminds of the incident.
Smile from justinchoo :-)