When something terrible happens, we call it a tragedy. This word is often used when the tragic event might have been prevented, or when the peope involved were unable to do anything to prevent the tragedy from happening.
It’s a tragedy that nothing was done to prevent the killer from getting his hands on some guns.
We all read about the tragedy online and in the newspapers.
As the tragedy unfolded, news trucks filled with reporters arrived at the scene.
The people of Syria deal with the tragedy of civil war on a daily basis.
The adjective form of this word is "tragic."
The death of the young woman was a tragic loss for her family.
After the country suffered a tragic military defeat, it learned from its mistakes and became a great nation once again.
The parents of the children dealt with their tragic loss through prayer and the comforting presence of family members.
Note: There are different degrees of tragedy, from the horriffic to the cataclysmic to the Biblical. When something is Biblical, the scale of the disaster is so large, it seems to many as if God might have had a hand in bringing it on or in limiting the number of lives lost.