Civilian casualties occurs in a general sense, when civilians are killed or injured by non-civilians, mostly law enforcement officers, military personnel, or criminals such as terrorists and bank robbers.
In general, a civilian is "a person who is not a member of the military or of a police or firefighting force", as defined by Merriam Webster's Dictionary.
A law enforcement officer or peace officer, in North American English, is a public-sector employee whose duties primarily involve the enforcement of laws.
Military personnel are members of the armed forces.
Caught In The Crossfire: Afghanistan's Civilian Casualties ... by VICE
Under the law of war, civilian casualties are civilians who perished or suffered wounds as a result of wartime acts.
The law of war is a legal term of art that refers to the aspect of public international law concerning acceptable justifications to engage in war and the limits to acceptable wartime conduct.
War is a state of armed conflict between societies.
Civilian casualties mount as Israel widens Gaza invasion by Al Jazeera English
In both cases, they can be associated with the outcome of any form of action regardless of whether civilians were targeted directly or not.