Question

Are mass murder and serial murder prevalent in societies not industrual

Answer 1

The answer to this question depends on how we understand "prevalent" - I understand it to be "very common", say present in around 80% of groups. 

I would say that this is not the case, the situation with murder is that it does not happen often, but the few cases of murder are well known so it seems like it happens more often that it does in reality. 

Another question is how do we understand murder - is killing during a battle a murder? in that case, in preindustrial societies wars were very common, and yes, then murder would be common too (but people don't typically understand killing in war to be murder)