"Murder is a habit"

Do you think that someone could actually get used to murder? It sounds crazy at first, but history suggests that humans can get used to practically anything. I mean, think about it. The first time you would kill a person, you would be absolutely traumatized and written with guilt. But the truth is, the first person to forgive you is actually yourself. I mean, at the end of the day, our brains were literally built to adapt to all phenomenon, no matter how bizarre. After someone kills, they experience a slight level of desensitization to the act as a whole. The next time a problem comes up, murder could even be a viable solution. It might even become desirable. Murder itself isn't exactly addictive, but the first kill weakens the psychological barrier greatly and the craziest part is, murder isn't the only thing that can become a habit. Humans are lazy, yet optimal. We often prefer the path with least resistance, even if it's not moral or correct. For example, someone who craves sexual intimacy could replace that with artificial pleasure. Repeat the cycle enough times and it doesn't become a choice. It just becomes an automatic response. It could even become as rudimentary as blinking or breathing.