I am not sure not saying anything to the children is helpful, children take these things in their stride.
I lived in Northern Ireland for 3 years in the early 90s,i had to explain to my children why we had armed guards on the camp gate,why the police often stopped and checked the car and pointed guns at us, why we couldnt go to certain towns on certain days and why they couldnt visit me and their new baby Brother in hospital.
They understood why, if the siren went off that we had to hide in the cupboard under the stairs, they knew that the loud bang they heard was a bomb going off,they knew Daddy had to check under the car before we were allowed near it and they coped with it all as it was just normal to them.
Give the children some credit. Dont lie to them or hide things from them, they are not stupid.