LAS VEGAS • Stephen Paddock's lethal attack on a Las Vegas country music festival on Sunday night was distinguished from most mass shootings by two features: the size of the arsenal he smuggled into the Mandalay Bay Resort and Casino and the great height from which he shot.
With a cache of 23 mostly powerful firearms, Paddock, 64, smashed the windows of his 32nd-floor hotel room and, from high above the Las Vegas Strip, sprayed bullets down on about 20,000 people listening to country music star Jason Aldean.
One of the weapons Paddock apparently used in the deadliest mass shooting in modern US history was an AK-47 type rifle, with a stand to steady it for firing, according to people familiar with the case.
The speed of the shooting led some to suggest the use of automatic weapons. But automatic rifles are heavily regulated and difficult to buy in the United States.
Instead, a so-called "bump stock" was used on at least two of the weapons, a legal attachment for a weapon that technically allows for it to count as semi-automatic even though it can fire up to 400 to 800 rounds in a minute.
In addition to Paddock's choice of weaponry, experts were struck by his decision to shoot at the concert-goers from high above, rather than walking through the crowd or firing from a nearby secluded spot on the ground. If Paddock had been on the ground, "he still would have killed a lot of people, but he would have been overtaken more quickly", said Dr James Alan Fox, a Northeastern University criminologist.
The tactic echoed two earlier mass shootings, most notably Charles Whitman's 1966 attack from atop the University of Texas Tower that killed 17 and wounded more than 30. A decade later, Michael Soles chose the top of a Holiday Inn hotel in Wichita, Kansas, to shoot and kill three people while wounding eight others.
But Paddock was far higher than either Whitman or Soles, and Las Vegas sheriff Joseph Lombardo estimated that he was shooting at victims at least 457m away.
When Paddock began firing, his victims were confused, defenceless and easy targets as police scrambled to find where the shots were coming from. First responders found Paddock after smoke from his rifles set off fire alarms in his hotel room.
Dr Adam Lankford, a University of Alabama criminologist who studies mass killers, said attacking from such a high location gave Paddock a tactical advantage that "rendered moot" everything Americans have been taught to do in mass shooting situations - to run from the gunfire, hide or even fight back if encountering the shooter.
Paddock also had the advantage of time, using multiple weapons and possibly reloading. The vast majority of active shooter incidents end within five minutes, with the shooter being stopped by police, bystanders or their own suicides, according to a Federal Bureau of Investigation study of attacks between 2000 and 2013.