Donald Harvey worked at many hospitals assisting ill patients...but he thought he had to kill them to put them out of their misery.

References:

http://allthatsinteresting.com

http://fox19.com

http://maamodt.asp.radford.edu

http://murderpedia.org

http://newpapers.com

http://nydailynews.com

http://nytimes.com

http://serialkillershop.com

http://upi.com

http://wtvq.com