Examining what led up to Manhattan shooting

In their search of the suspect's car located at the scene, police found medications, along with a rifle case with the rounds and a loaded revolver and more ammunition. Anna Schecter is joining us now. She's the senior coordinating producer for CBS News's Crime and Public Safety Unit. Anna, today, the mayor addressed the note left by the shooter. You got a copy of that note. What did it say?

That's right. He listed out CTE and the full medical term for it. He blamed the NFL for putting profits over the health and safety of players in the NFL. He even listed the name and the method of suicide used by a former NFL player, who later it was determined through a study of his brain that he had CTE. So this was, investigators believe, the driving force, what led him to drive across the country with this semiautomatic weapon and carry out this attack.

So on that drive across the country from the Las Vegas area to New York City, what have law enforcement officials said about how that happened and how he was able to make his way here?

Well, we actually have traffic camera, still images of that black BMW car at different points. So that's how we were able to show our viewers that map right there, because his car and that license plate pinged a number of times. So he would stop, refuel for gas. And there were innocent civilians probably interacting with him that whole time who had no idea that he was going to carry out this attack, but investigators are retracing his steps and trying to interview anyone who might have had a clue of what he wanted to do.

We also know about what he had in the car in terms of weapons, right? But you've been reporting about the weapon that he used specifically in the attack. What have you learned?

Sure. Well, we saw that image of him just brazenly walking across the plaza with this semiautomatic weapon. It's a Palmetto State Armory, PA-15 rifle. We have the serial number because the ATF stepped right in. They're tracking who purchased the gun. We know who purchased the gun. It was initially owned by his former supervisor at the Caesars Palace Horseshoe in Las Vegas, Nevada. So we have all of that information. Our law enforcement sources believe that that weapon was actually legally transferred from his former supervisor to him in the last few years. All amidst new information that he was having mental health struggles. He even called the police with suicidal ideation. And yet his concealed carry permit was not taken away from him.

Wow, such important reporting. Thank you so much, Anna Schechter. We appreciate it. Of course.