1) Don't ignore the questions or feelings they have! Talk about them; better yet, let them talk and you listen.
2) Seek out answers together as a family through prayer and reading God's Word.
3) Use them as a teaching time to instill Godly character and teach them about God Himself.
4) Look for ways to help someone personally affected by the tragedy. In this case, contact the Red Cross and see how to best help.
"Faith is more often caught, not taught."