Expert: Vegas gunman legally altered weapon to fire like machine gun

A gunman who killed more than 50 people in Las Vegas had more than 40 firearms – and some were likely modified to fire like automatic weapons.

Investigators say Stephen Paddock had 42 firearms in the hotel room and his home, but they have not said what types of guns have been recovered.

The horrific sounds of rapid-fire gunshots are unmistakable to retired 30-year ATF veteran Hector Tarango. Police sources tell FOX 4 that two rifles out of the 23 guns found inside Paddock's hotel room had modified stocks that could have made them fully automatic.

"From what I saw when I saw the clips, it was very clear to me that it was automatic gunfire,” Tarango said. “Again, could it be the bump fire?  That's a very strong possibility based on what I researched that I've done."

Tarango is describing a particular accessory called a bump stock. Even though it makes a gun similar to a fully automatic machine gun, he says it’s legal because it does not alter the internal trigger or slide mechanisms of the weapon. With training, the gun fires just like a fully automatic rifle.

The Clark County sheriff also says a low-grade explosive called Tannerite was found in Paddock's car.  It's typically used for long range target practice and explodes when a bullet hits its target. But when misused, it can be deadly.

"I've seen where they've blown up a washing machine and shrapnel comes back a hundred yards and hits the shooter,” Tarango said. “So it's very troubling to see it in that particular instance in what he was trying to do in killing all these people."

The 42 guns seized from the hotel room and Paddock's home have been sent to the FBI lab in Quantico, Virginia, to be analyzed.

Police sources also tell FOX 4 there is video online indicating Paddock was a skilled shooter. But there's no evidence so far that he purchased any guns illegally, including a shotgun from a store in St. George, Utah.

Dixie Gunworks Owner Chris Michel says Paddock underwent a background check and was cleared by the FBI to make the purchase. He says nothing stood out about him.

"Just a normal everyday customer. Walked in the doors. Came in three or four different times looking around. Average everyday Joe Blow,” Michel said. “No red flags. Nothing to that effect. Came in, ended up purchasing a shotgun. It took him three separate visits to purchase the shotgun."

Tarango says the bump stock used to be $250 to $300 when they first came out. But he says now they can legally be purchased for $100.