CreedTheChimera said
The perfect example is his first victim, a nurse that would overdose people on morphine and something else. When he subdued her, she kept insisting she was 'helping' them, right until the end.
A psychopath. Mentally ill. However, it can be cured. Sometimes, a psychologist can help one of these people. People can convince themselves of almost anything if they feel they have to, or if their mind makes them. Psychologists are here to help people with problems like that.