At least 58 people were killed and more than 500 others injured after a gunman opened fire Sunday night at a country music festival across the street from the Mandalay Bay Resort and Casino on the Las Vegas Strip, authorities said.
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Investigators found fully automatic guns among multiple weapons in Stephen Paddock's 32nd-floor Las Vegas hotel room, according to the top Democrat on the House Intelligence Committee, Rep. Adam Schiff.
The congressman from Burbank, who received a briefing from FBI officials in Washington on Monday, said he didn't know if the guns found in the Mandalay Bay Resort room were manufactured to be fully automatic or had been modified. Such weapons fire more than one round with each pull of the trigger.
Paddock killed himself as SWAT units converged on the room amid Sunday night's carnage, officials said.
The FBI has sent investigators and crime scene technicians to help local authorities sift through the large crime scene, interview witnesses and chase down investigative leads, Schiff said.
Sheriff Joe Lombardo of Clark County, which includes Las Vegas, is in charge of the investigation into the worst mass shooting in U.S. history. At least 58 people were killed and more than 500 injured in the attack targeting an outdoor country music festival on the Las Vegas Strip, within view of the Mandalay.
Private citizens can legally own fully automatic weapons made before October 1986 after submitting to a federal background check and applying for a license from the Bureau of Alcohol, Tobacco and Firearms. It is also possible to convert a semi-automatic rifle into an automatic machine gun.
Newly manufactured fully automatic weapons are more heavily regulated by ATF and can only be sold to some federal and state agencies.
So far, authorities don't know what prompted 64-year-old Paddock, a resident of Mesquite, Nev., to repeatedly fire into the concert crowd, Schiff said. The Islamic State claimed responsibility, but Schiff said the group often takes credit for attacks it wasn't involved in; the FBI had said Paddock had no apparent connection.
"We don't know the motives of the shooter yet," Schiff said.
"It's staggering to try to wrap your mind around how many people were killed," Schiff said. Incidents like this are made "all the more lethal because of access to automatic weapons," he added.