American Psychological Association - Talking to Children About Difficult News
American Academy of Pediatrics - Talking to Children about Tragedies & Other News Events
From Common Sense Media https://www.commonsensemedia.org/blog/explaining-the-news-to-our-kids
Tips for kids under 7
Keep the news away. Turn off the TV and radio news at the top of the hour and half hour. Read the newspaper out of range of young eyes that can be frightened by the pictures (kids may respond strongly to pictures of other kids in jeopardy). Preschool kids don't need to see or hear about something that will only scare them silly, especially because they can easily confuse facts with fantasies or fears.
Stress that your family is safe. At this age, kids are most concerned with your safety and separation from you. Try not to minimize or discount their concerns and fears, but reassure them by explaining all the protective measures that exist to keep them safe. If the news event happened far away, you can use the distance to reassure kids. For kids who live in areas where crime and violence is a very real threat, any news account of violence may trigger extra fear. If that happens, share a few age-appropriate tips for staying and feeling safe (being with an adult, keeping away from any police activity).
Be together. Though it's important to listen and not belittle their fears, distraction and physical comfort can go a long way. Snuggling up and watching something cheery or doing something fun together may be more effective than logical explanations about probabilities.