system
A chat on subreddit /r/NoStupidQuestions
human
I suspect they are under represented in the serial killer numbers. Angel of Mercy killers are not unknown in the medical fields and tends to be really hard to track down.  In a field where a breakdown of information flow, or equipment can cost a life it can be very difficult to find the cause of it. 

And we have about 400k deaths from medical mistakes a year, so it is not as if there is a lack of dead bodys and nursing is a female dominated industry.
gpt
This is a terrifying thought.