So in Episode 6, Mon Mothma says that "many" Bothans died to bring them information about the Death Star project and installations. I don't remember much about the EU, but wasn't there an event where Bothans who were part of their Spynet and retrieving information relevant to the Death Star were used as part of an Imperial trap somehow and got shot up? (I might be misremembering and they might not have been working on Death Star-related information - sorry, it's been a while!) That's a room full of slicers at most, I'm not sure it counts as "many."
Is this all that Mon Mothma is referring to, or is there some other incident of Death Star information-related Bothan mass deaths?