He is older than the typical mass shooter/mass murderer as most have been in their late teens or twenties and many came from affluent families.
Also, his killing spree was an extension of an initial crime he had committed and not a stand alone crime as other mass shooters/mass murderers who targeted a specific group of people in a specific controlled environment.
Malvo and Mohammed didn’t fit that “profile”, either, IIRC.
Maybe, sometimes, there is no profile.
Read about his entire criminal history.
He killed two other people along with animal torture.
http://www.kansascity.com/news/local/crime/article1575841.html