This word is interesting in that it has three potential meanings.
First is as a person or thing that is lost injured or destroyed. Which is how you have probably heard it used the most. Someone who is lost or wounded in an event is usually counted as a casualty. It can also broadly mean “victim” with no real violence required. Someone who loses their job due to downsizing can be considered a “casualty” of declining fortunes.
The second, which we still hear from time to time, is defined as a serious or fatal accident. So the event itself. Which you may have seen when shopping for insurance. For example, the company named Bankers Life and Casualty Company or when reading your policy and you see the P&C line: Property and Casualty. if I fall down and break my leg at your house it would be covered under your casualty insurance.
The third one and the one that is the origin for all of them dates to the 15th century and means “chance or fortune”. This can be traced to Late Middle English and all the way back to the Latin casualtias and casualis that translates to casual. Which kind of make sense.
So yes, when they give a list of casualties they are basically saying that the people were hurt by chance or mere fortune or at least casually. Yikes.