Mexico has a particularly low suicide rate; and, an illegal who has the get up and go to come here for work would be less likely to attempt this act. Generalizations, I know, but just my 2 cents...
According to accounts I've seen and heard in local media, the perp appears to have been on an accelerating downward spiral due to drug abuse. He was starting to become violent with his wife, so she and her family threw him out. His own family says they didn't want to have anything more to do with him. He has all the earmarks of the type of mass killer who snaps one day and shoots up a business or school before either taking his own life or being killed by cops.