No details were available officially until Tuesday on the weapons that Stephen Paddock used to kill at least 59 people and wound 527 late Sunday in Las Vegas, apart from the fact that 23 firearms were found in his hotel suite. There were AR-15 assault-style rifles, which is a semiautomatic version of the US military’s M16 rifle. A semiautomatic fires a single round each time the trigger is pulled; automatics, on the other hand, can keep firing continuously with a single squeeze of the trigger. Automatic rifles are highly regulated — regulations for semiautomatics vary from state to state — and some of Paddock’s semiautomatic rifles may have been modified to make them fully automatic. The rapidfire sound in witness videos indicates that at least some weapons had rapidfire capabilities.
Fire and rapidfire
In one particular 15-second video of the Las Vegas carnage, about 90 shots can be heard in 10 seconds (9 rounds per second). By contrast, audio extracted from a video of the June 2016 Orlando nightclub shooting, in which 49 people were killed and 53 wounded, has 24 shots in 9 seconds (fewer than 3 per second). The Orlando shooter, Omar Mateen, used at least two guns, including a semiautomatic AR-15-style assault rifle.
Finally, audio of a fully automatic pre-1986 Colt AR-15A2 comes through as being without any variations in firing rate, shooting 98 shots in 7 seconds (14 rounds per second). (In 1986, Congress barred civilians from buying or selling fully automatic weapons made after that date, although individuals can legally possess older weapons after passing a background check and obtaining a special permit. There are about 176,000 pre-1986 machine guns registered with the government that can be legally transferred, and they typically cost tens of thousands of dollars.)
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Bump fire stock
The Las Vegas shooter could have modified his weapon to fire faster, using a trigger crank (a mechanical add-on that is rotated like a music box handle and hits the trigger multiple times per second) or a bump fire stock (which uses the recoil of the rifle to fire quicker). Neither device is regulated by the US National Firearms Act.
Two officials familiar with the investigation told The Associated Press that Paddock had two bump stocks. Whether those stocks were used to modify the weapons used in the massacre, was being investigated. Which weapons were used will be determined based on factors including the spent cartridge cases in the hotel suite.
Bump stock devices, which essentially convert semiautomatics into automatics, have faced scrutiny of late. The device basically replaces the gun’s shoulder rest with a “support step” that covers the trigger opening. By holding the pistol grip with one hand and pushing forward on the barrel with the other, the shooter’s finger comes in contact with the trigger. The recoil causes the gun to buck back and forth, “bumping” the trigger.
Technically, that means the finger is pulling the trigger for each round fired, keeping the weapon legally a semiautomatic. Once “bumped up”, such a semiautomatic can fire at a rate of 400 to 800 rounds per minute.
The duration of the bursts, as recorded, suggest that Paddock cared little about the military’s prescriptions for automatic fire. Sustained rapid fire is difficult to control and causes many weapons, especially light weapons, to overheat quickly.
The length of the bursts also indicate that Paddock had magazines capable of holding scores of rounds, allowing him to fire longer without reloading.
Nevada, unlike some states, has no laws limiting ammunition magazine capacities.
Firing from a height
Paddock fired from a 32nd floor hotel room, across an urban area, into a crowd about 500 yards (a little less than half a kilometre) away. It was not an easy, but his preparations made it possible for him to inflict mass carnage.
According to law enforcement officials, Paddock established firing positions by smashing a pair of windows in his room. In his arsenal were rifles designed to be fired at such distances. From his high perch, he could aim over objects and obstacles that might typically come in the line of fire from a lower height and was, therefore, more likely to strike with even errant shots than he would be from ground level.
It is possible that he used tripods, which officials said were in the room. Special mounts designed to fit the underside of a rifle and sit atop camera tripods allow the gunman to fire more accurately while standing. Military snipers use tripods in urban spaces, often setting themselves back from a window so neither they nor their weapons can be seen from the streets below.
Two law enforcement officials said Paddock used a hammer to break the windows through which he fired, and the sheriff said he possessed scopes for at least some of his weapons, though it was not clear what roles they played.