It transpires that Las Vegas gunman Stephen Paddock fired “incendiary” bullets in an attempt to explode a tank of jet fuel in his attack on concertgoers at a country music festival. Paddock, 64, fired the special ammunition – meant to ignite upon contact – at a 43,000-barrel fuel tank at the McCarran International Airport near the festival.

The rounds were recovered in Paddock’s room at the Mandalay Bay Resort and Casino. Airport officials confirmed that two rounds did hit a tank of jet fuel, with one actually penetrating the tank, but did not confirm that these were incendiary rounds.

Officials last week downplayed the possibility of any explosion triggered by gunfire, given designs meant to withstand brief exposure to flame.

Crime Scene Investigators also found “tracer” rounds in the hotel, which are used to illuminate the path of the bullet and improve accuracy in low visibility.

But the plot was doomed to failure from the start as Jet fuel is relatively hard to ignite burning at between 800 and 1,500 degrees Fahrenheit. Mike Boyd, an aviation analyst for Colorado-based Boyd Group International, said “I used to train hazardous-material instructors at airports, and one of the things we taught was that if you even if took a blowtorch to a bucket of standing jet fuel, it would take about 90 seconds for it to want to burn,” Boyd said.

In addition, jet fuel requires a massive ratio of fuel to air for even its flammable vapour to combust. To ignite 17 ounces of jet fuel, for example, it would have to be atomised, (mixed in) with 1,000 ounces of air.”

The new twist on the mass shooting may highlight some vulnerabilities of airport fuel tanks, which often stand out in the open with little or nothing to shield or conceal them, but it also reinforces why they’re aren’t necessarily a security priority, Boyd said.

“They just aren’t good targets for terrorism,” he said.