Police in Las Vegas have not yet offered details of the weapon or weapons used by the gunman in the Mandalay Bay Resort, but audio recordings of the mass shooting suggest that at least one automatic weapon might have been involved.
The gunman opened fire from a high floor of the hotel on an outdoor concert festival Sunday night, killing more than 50 people and wounding hundreds of others in one of the deadliest mass shootings in U.S. history.
The limited information available so far raises a host of technical questions, including whether the gunman had a machine gun or a military-style assault rifle, or both. Both classes of weapon have the range to reach the concert from the shooter’s hotel room and can fire multiple bullets with a single depression of a trigger, in what are commonly called bursts.
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Weapons capable of burst fire have long been federally regulated in the United States and are much more difficult to obtain than weapons that fire semi-automatically, for which regulations vary by state.
In some videos of the shooting, the rate of fire sounds inconsistent, at times sputtering. This suggests another possibility: that a weapon could have been modified to fire faster, a change to a semi-automatic firearm known as bump or slide fire. Such modifications harness the recoil to allow for rapid fire.
The duration of the bursts in Las Vegas, as recorded, also suggest that if the shooter had military or other formal weapons training, he did not follow it. Conventional military training emphasizes brief, controlled bursts of fire, not the extended bursts heard in Las Vegas.
Bursts of that duration are difficult to control and cause weapons to overheat, often quickly.
Authorities identified the gunman as Stephen Paddock, 64, of Mesquite, Nevada.
Maj. Dave Eastburn, a Pentagon spokesman, said Monday morning that the branches of the military were checking their records to see whether Paddock had served in the armed forces.
How the gunman organized logistically for the attack raises still more questions. It was not yet clear, for example, whether Paddock fired more than one weapon, used iron sights or optical sights, changed barrels, or how much ammunition had been prepared in ammunition belts or magazines before the crime.
Nevada, unlike some states, has no laws limiting ammunition magazine capacities, meaning the shooter could have purchased equipment locally that could hold scores of rounds, allowing him to fire longer without reloading.
Preliminary reports from Nevada also indicate the shooter had stayed in the room for several days, which would have allowed ample time to create, or at least plan for, a shooting position allowing him to stabilize a weapon — potentially improving accuracy despite the high rate of fire.
More than 10 rifles were found in the room, Las Vegas Metropolitan Police Department Sheriff Joseph Lombardo said at a news conference Monday.
The range at which the shooting occurred, roughly 400 yards from the resort to the concert stage, and longer to many areas where the concertgoers had congregated, was at the long end for many military-style rifles but average for light machine guns. The density of the crowd would mean that even relatively inaccurate fire would strike many.