I would post a link, but I am not sure how to do that.
According to the Post, the shooter carried a several pages note, which may shed some light on his motive for the mass shooting.
He had a beef with the NFL. He seemed to believe that he had a chronic traumatic brain injury. As to why he went to the 33rd floor, which was the floor for the corporation which built and owns the building, instead of the 5th floor, which houses the headquarters for the NFL, is unknown.
The Wikipedia entry for that kind of brain injury says that it has been found in 99 percent of the brains of deceased NFL players, and is believed to be caused by repeated blows to the head, including blows not leading to a concussion?
The note that the shoote supposedly carried asked for his brain to be studied.
Scary, tragic, and sad.
The Wikipedia article also said that the condition leads into a progressive form of dementia.
The other information they had said the shooter worked in a casino and lived with his parents in a upscale gated community.