Can we believe them and why would we? For months now the militants of the so-called Islamic State have toyed with their hostages—journalists and aid workers among them. They have claimed they are alive when they had already slaughtered them. They have used their captives mercilessly as pawns in a grisly information war, torturing their families from afar in the process, all in an effort to manipulate and goad the countries they come from and to sow fear.

So skepticism has greeted the terror group’s claim in a tweet today that a female American hostage the militants have been holding for more than 18 months was killed in a Jordanian airstrike. In that statement circulating on Twitter, the Islamic State said air raids outside the northern Syria city of Raqqa—one of a wave the Jordanians have mounted since the militants slaughtered one of their pilots—was responsible for the death of the 26-year-old Kayla Jean Mueller. She had gone to Syria to help children orphaned in the war— hardly a bellicose action.

“The criminal Crusader coalition aircraft bombarded a site outside the city of Raqqa today at noon while the people were performing the Friday prayer,” the militants claimed. “The air assaults were continuous on the same location for more than an hour,” it added. The militants shared three photographs of a wrecked building that it said had come under attack.

The ISIS claim is that Mueller had been inside the building at the time of the airstrike, which oddly had failed to injure any of her guards. But they provided no other photographic evidence—other than the bombed-out building. And it curiously had no smoke billowing from it and could have been struck earlier this week or even before. The group said the woman was killed by “fire of the shells dropped on the site.”

Only days ago, the Islamic militants, while negotiating for the release of a terrorist jailed in Jordan, failed to provide proof of life of Jordanian pilot Muadh al Kasaesbeh. He, of course, was already dead, and had been since early January, according to British and Jordanian officials.

Now, at the time of this writing, ISIS has failed to offer proof of death for Mueller, prompting Jordanian officials to question whether the militants are using an old tactic of claiming a hostage had been killed by their own side, when in fact those responsible for the death were the captors themselves.

If the aid worker is dead, it seems highly convenient for the militants that it was a Jordanian airstrike that claimed her life. And how do they know this—how do they know it was a Jordanian warplane rather than an American one that dropped the bomb or fired the fatal missile?

(Officials with the U.S.-led military coalition told The Daily Beast Friday that they've conducted no airstrikes inside Raqqa since ISIS aired its snuff film of the pilot earlier this week.)

Also highly convenient is the manner of the claimed death: by fire. That trope has been used before with the way the militants put to death al-Kasaesbeh. The pilot brought fire and dropped incendiary bombs; so he should die in flames, an appropriate retaliation, as far as ISIS leaders see it, and according to a principle known as “qisas”, a law of equal retaliation.

Some officials in the international coalition already suspect that the ISIS claims of Mueller’s death and how she died are just another effort to drive a wedge between the Americans and Jordanians, the aim, too, of the sadistic burning to death of al Kasaesbeh.

According to Shiraz Maher, a Senior Fellow at the International Centre for the Study of Radicalization at King’s College, London, ISIS has been seeking to leverage the hostages it has been holding to “asymmetrically shock” and confuse its enemies. With the unbelievably vicious killing of al Kasaesbeh ISIS leaders appeared to be aiming at deterring Jordan from continuing to back the U.S.-led coalition against them.

So far that tactic appears not to be working—in fact, it has had the reverse effect. Jordan has increased its military role and sworn to avenge every single hair of the dead pilot. And the increased airstrikes are “the beginning of our retaliation,” promises the country’s Foreign Minister Nasser Judeh. “We’re upping the ante. We’re going after them wherever they are, with everything that we have,” he says.

Thousands rallied in Jordan’s capital, Amman, Friday morning in support of their government’s fierce military response. Pro-Islamist opposition within Jordan to the role the kingdom is playing against ISIS appears, at least for now, to be intimidated by the cruelty of the pilot’s slaying.

There have been hopes that Mueller would eventually be traded—or even just released. ISIS has previously not harmed Western female captives—although it has not been as restrained with the non-Western women from groups deemed foes that have fallen into its hands. In line with their atavistic interpretation of the Quran, the militants have kidnapped and enslaved more than 2,500 Yazidi. Another 2,000 are missing. Local women accused of adultery have been stoned to death.

But according to onetime ISIS hostage Didier Francois, a French journalist, Western female captives held by the militants were during his time in captivity better treated than the men—not beaten, not shackled and allowed a little more movement. That prompted the hopes of her eventual release.

Now mystery is likely to surround what befell the aid worker from Arizona. Much as it still does with the death of another Western humanitarian worker, Margaret Hassan, an Irish woman, who was abducted and murdered in Iraq in 2004. Her kidnappers have not been identified. Her remains never recovered.

In a video released of her during her captivity she begged then British Prime Minister Tony Blair to withdrew British troops from Iraq, saying “these might be my last hours.” Al Jazeera reported her kidnappers threatened to hand her over to the group led by Abu Musab al-Zarqawi, the mentor of ISIS leader Abu Bakr-al Baghdadi.

-- with additional reporting by Nancy A. Youssef