From two interviews with people who met him:
The University of Colorado doctoral student said Holmes' fellow grad students were as shocked as anyone.
"We all think the same thing as everyone - that he was pushed past his breaking point," the young man said. "But I, personally, don't know what that breaking point was."
Holmes, he said, complained over beers about academic pressure, just like the other students did. But within his small circle of doctoral student friends and classmates, that was not unusual.
I'm sure his "failure" in grad school was disappointing. Too early to say if it contributed to what happened.
There is also a 2nd report of a racial outburst, and an apology that suggests Holmes knew it was socially unacceptable (the previous outburst was at a bar while he was intoxicated - it doesn't seem he apologized for that one from what I've read). Where the racial outbursts come from despite the fact that he seems to know they're not socially acceptable is unclear at this point.
LIQUOR STORE OUTBURST
The first time shooting suspect Holmes walked into Original Aurora Liquor - about four blocks from his Aurora apartment - a year ago, a Palestinian immigrant who works behind the counter mistook him for an Iranian.
"Are you Iranian?" employee Joseph Nasser, 50, asked Holmes, who he said became visibly angry.
"What?! I'm no (expletive) Iranian," Holmes replied, according to Nasser, who has worked at the store seven years.
Nasser said Holmes looked like an Iranian customer who frequented the store at the time.
The next time he came in, Nasser said, Holmes apologized for his outburst. Nasser said Holmes came in a number of times over the past year, alone as best he could remember, and would usually buy a six pack of beer.