First, who among us Chinese would have the kind of military training to handle two gun? Stuff like automatic clips. He was also very calm and calculated. Unless he was graduated from a military school or something, ordinary Chinese would not have that kind of training.
Second, how would some young fellow, a few months in the US knew so much about the system. He knew where to get his gun and he knew to send in bomb threat a couple of days ahead so he could watch the emergency resonse.
Not to say people like this don't exist, but people like this hardly go nuts in my opinion.