>Is it surprising he was a loner? Isn’t that very consistent?

Criminology experts should jump in here, but I don't think introversion is a good predictor of violent criminals. I don't know if people with "creepy" personalities are more likely to become loners, but I suspect it's more complicated than that:

https://www.psychologytoday.com/us/blog/quiet-the-power-introverts/201105/the-myth-the-killer-introvert

Colbert used this in the Late Show cold open this evening (not yet on YouTube).
Edit: https://www.youtube.com/watch?v=zt4eVA0Rz7c