What We Don't Yet Know About The Las Vegas Attacks

Las Vegas shooter Stephen Paddock's motives are a mystery a day later, and the extent of his arsenal isn't public. NPR's Tom Gjelten looks at those and other questions that don't yet have answers.

ROBERT SIEGEL, HOST:

Joining me in the studio is NPR's Tom Gjelten, who's been following this story from Washington as best he can. And, Tom, we've heard just in the past hour confirmation from the FBI to Congressman Adam Schiff that at least some of the weapons that were taken I guess from the hotel room were not just semiautomatic weapons but fully automatic weapons. First, what's the significance of that?

TOM GJELTEN, BYLINE: Well, a fully automatic weapon can fire continuously. You pull the - you pull the trigger and it fires continuously. It's basically a machine gun. There's effectively no difference between a fully automatic weapon and a machine gun. Now, machine guns or fully automatic weapons are - they're not quite illegal, but you have to have special permission from the Treasury Department to have one. They're very rare, actually. Police very rarely find them. My understanding is that we don't have any recent mass shooting events that have used a fully automatic weapon. They're obviously far, far more lethal.

SIEGEL: As we heard at the beginning of the hour, the police on the scene initially called it automatic...

GJELTEN: Right.

SIEGEL: ...Because they heard the rapidity of the gunfire and it didn't sound like a semiautomatic weapon.

GJELTEN: And you just played it at the beginning of the hour, right. So you can tell just by listening to that that is not the rate of fire that you can get by pulling the trigger individually for each - for each shot. So even though they had not at that point seen the weapons they could tell just by the sound, as you say, that they were automatic.

SIEGEL: And so a big question then is, did the gunman manage to acquire weapons that were fully automatic, that had been adapted to be fully automatic? Or did he purchase weapons that are more accessible and legal and have them fixed?

GJELTEN: That's the part that we don't know. We'll undoubtedly find the answer to that in the coming days. It is possible to modify a semiautomatic rifle to a fully automatic. One of the things that the sheriff mentioned is that they're looking at whether the sear pins were filed. Now, the sear pin is actually that part of the trigger mechanism that can determine whether it's automatic or not. And if you file it down, you can take a - you can make a semiautomatic weapon into an automatic one. We don't know - first of all, it's probably doubtful that he had the expertise to do that. But he could have worked with some unscrupulous gun dealer who had those weapons already modified.

SIEGEL: NPR's Tom Gjelten. Thanks, Tom.

GJELTEN: You bet.

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