It's often difficult to know what to say, especially to young children. Here are a couple of links to sites that offer ideas for how to talk with the children in our lives:
This was developed by the people who bring us Sesame Street, with characters that your child may be familiar with. Elmo's voice may be a good counterpoint to the 24 hour news cycle.
Another resource comes from the Unitarian Universalist Association and has links to a number of sites:
There are many other resources available to us. The most important thing is to begin the discussion, and thus the healing.
Much love to you all.