I believe "W' changed that.

No word yet on the total number of people shot.

And they say there's a car in the area with Nevada plates.

Someone had a very specific beef.

The New York Post said that a note, several pages long, was found on his body. It may shed some light on his motive for the shooting.
He may have believed that he had a traumatic brain injury, which is believed to be caused by repeated blows to the head. It's frequently found in people who play rough contact sports, such as football.
The Wikipedia entry that I found for the specific injury said that it has been found in 99 percent of the brains of deceased NFL players.
The shooter requested, in his note, for his brain to be studied. Wikipedia says the condition caused by the repeated blows to the head can only be properly diagnosed through an autopsy.
I know I will probably get chastised for speculating, but I think that your guess is correct.

Watching Rachel about this story now. Horrible situation.

4 people killed. Horrible.

...2nd Amendment rules! Blah blah

Too early to discuss gun control, blah blah.

History of mental problems, blah blah.

In many ways, this country sucks.

https://russblib.blogspot.com/?m=1

Link to tweet

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.

Thank you, however, for responding, and for providing a link.

NT.

and NYS passed the SAFE Act in 2013 which not only bans assault weapons, but also prohibits the mentally ill and anyone who is under an order of protection from buying any gun. Background checks are required, including for private sales. The PBA is still lobbying for a national ban.

Not only would the gunman not have been able to buy any type of assault weapon in NYS, he would not have been able to purchase any weapon whatsoever due to his history of mental health issues.

Good On New York!

So he was allowed to buy a gun and travel across the country to shoot a bunch of people? What a country we live in!

...walking into the building to kill people. Horrible incident, tragic---but why would we ever be surprised by things like this, given the way this country is being run, and by whom?

In Texas, you need to be determined "incompetent" by a judge, which is a high bar. You can also be denied a firearm for various felony convictions etc. You are more likely to be barred from owning a gun due to a criminal conviction, than mental illness. That's because mental illness needs to meet a legal threshold and not just a medical medical diagnosis. Although there are more people with mental illnesses than convicted felons, a doctor just can't call authorities on everyone that is being treated. Doctors are reluctant to take legal action against their patients.