With regards to motive, Faisal fits what is the common profile of the Islamic terrorist that operates in North America.
Fairly well educated from a middle to upper-middle class family. I would suspect his father pushed him fairly hard towards schooling to the exclusion of a social life or other extra-curricular activities. Once out of school life proved somewhat disappointing work-wise. He didn't make any friends because the mechanisms for outside relationships was never cultivated in their youth. These are the kinds of people who wind up in the jihad sub-culture.
President Clinton rightly identified this phenomena years ago. It's an adverse reaction to globalization in general and the westernization of the world in particular. You might think that it's in reaction to some event like drones or Americans in the Middle East but it's really not the case. Weak-minded Muslims drift into radical Islamic organizations just like westerners might wind up in Scientology or Christian fundamentalist camps. It's to belong to something, it's personal. These people are lost in modern society.