A lot of those things were cleared up for me when I visited the site in Dallas. People claiming conspiracy are trying to make what he did much more difficult than it really was. He had a job that happened to be in the right place at the time, he had a standard gun anyone could buy, and plenty of time alone (he specifically did not have anything on his todo list for the day done despite being at work for a few hours). There is nothing about this a lone actor would have any trouble with, other than the initial luck of getting a job there in the first place and that type of coincidence isn't unlikely.