I am, frankly, shocked to learn that serial murder by healthcare professionals is a LOT more common than I had ever imagined. I am even more shocked to learn that they often see it as humane euthanization. It's amazing how people can get twisted around to rationalizing atrocity.
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1556-4029.2006.00273.x
A study on this subject. Between 1970 and 2006 they were able to find a total of 90 healthcare professionals who were charged with medical murders. Not all were convicted.
Modern Life Has Made It Easier for Serial Killers to Thrive
Another good article. About 40% of murders are unsolved. The authors conclude that there are 2100 or so active serial killers in the US at any given time.
So most of us are not out there killing people.