I am just beginning to look more into Roman history so I'm not sure if this is common knowledge or not. I think I remember reading somewhere that a lot of civilans were murdered by Caesar (his forces) in Gaul. Is this true and if it is, are there any estimates on number of people killed?
I found this old thread that addresses a somewhat similar question. I hope this is allowed here.
Specifically /u/Celebreth provides a lot of sources in their answer as well, which may help you.