Days after the Islamic State group’s leader, Abu Bakr al-Baghdadi, and his heir apparent were killed in back-to-back attacks by U.S. forces in northern Syria, the group broke its silence Thursday to confirm their deaths, announce a new leader and warn America: “Do not be happy.”

In an audio recording uploaded on the Telegram app, the Islamic State mourned the loss of al-Baghdadi, who led the organization for nearly a decade, and its spokesman, Abu Hassan al-Muhajir, who was killed a day after al-Baghdadi and who had widely been considered a potential successor.

The audio recording was the first word from the Islamic State confirming the death of its leader, which President Donald Trump triumphantly announced Sunday as a huge blow to the world’s most fearsome terrorist group.

Trump and Pentagon officials said al-Baghdadi had blown himself up with a suicide vest, also killing two children, after he had been cornered Saturday in a dead-end tunnel during a U.S. military raid in a northern Syrian village. Al-Muhajir was killed Sunday in an airstrike elsewhere in northern Syria.

Al-Baghdadi’s death came eight months after U.S.-led forces in Syria seized the last remnants of the territory once held by the Islamic State, which at its height spanned an area the size of Britain across parts of Syria and Iraq.

The Islamic State announcement said that al-Baghdadi had been succeeded as leader by Ibrahim al-Hashemi al-Qurayshi, whom it identified as the “emir of the believers” and “caliph.”

Almost nothing is publicly known about al-Qurayshi, including his real name, and counterterrorism analysts were scrambling Thursday to try to figure out who he is.

“Nobody — and I mean nobody outside a likely very small circle within ISIS — have any idea who their new leader ‘Abu Ibrahim al-Hashimi al-Qurayshi’ is,” Paul Cruickshank, editor of the CTC Sentinel at the Combating Terrorism Center, said in a tweet Thursday. “The group has not yet released any meaningful biographical details which might allow analysts to pinpoint his identity.”

Daniele Raineri, a journalist and analyst who has been studying the Islamic State’s leadership structure for more than a decade, said that the group’s leaders often acquire a new nom de guerre with the appointment to a new position, meaning al-Qurayshi may have had a completely different name last week.

The al-Qurayshi appellation at the end of his name indicates that he is being portrayed as a descendant of the Quraysh tribe of the Prophet Muhammad, a lineage that the Islamic State considers to be a prerequisite for becoming a caliph or ruler of a Muslim theocracy.

Its use indicates that the Islamic State continues to see itself as a caliphate — even if one with practically no territory.

“It shows that while the world is ready to pronounce the Islamic State dead and finished, the group’s core leadership continues to believe it can operate much as it has in the past,” said Colin P. Clarke, a senior fellow at the Soufan Center, a research organization in New York.

“The suggestion is that nothing changes, allegiance should still be to the leadership, and affiliates and franchises should continue to look to al-Qurayshi for guidance on how to operate,” he said.

The announcement, in a seven-minute, 37-second recording, was coupled with a warning to the United States not to gloat over killing al-Baghdadi, who oversaw beheadings of American hostages and other atrocities.

“Do not be happy America, for the death of Sheikh al-Baghdadi, and do not forget the cups of death at his hands, may God accept him,” the announcement said.

It boasted of the group’s disciples and expansion beyond the Middle East, even as its core territory in Iraq and Syria was reduced to nil: “Don’t you see America that the State is now on the threshold of Europe and Central Africa?”

Records of wire transfers and the testimony of captured fighters in the Democratic Republic of Congo indicate that the group has set up a base of operation in the Central African country.

The announcement also took aim at the leadership of Trump, admonishing the United States: “Don’t you see how you became the laughingstock of the nations, and an old and crazy man controls your fate, whose opinion changes between morning and evening?”

The announcement implied that the Islamic State hierarchy had convened in order to discuss the successor question and suggested that he had been hand-picked in advance by al-Baghdadi: “The sheikhs of the mujahedeen agreed, after consulting with their brothers and acting upon the recommendation of Abu Bakr al-Baghdadi, to pledge allegiance to the sheikh and mujahid, the scholar, doer and worshipper Abu Ibrahim al-Hashemi al-Qurayshi,” the announcement said.

Devorah Margolin, a senior research fellow at George Washington University’s program on extremism, said that the fact a shura, or governing council, had selected the new leader “shows the ISIS bureaucracy is still in place.” She added: “We should not underestimate them.”

The announcement also called upon supporters to pledge allegiance to the new leader, a ritual that took new meaning under al-Baghdadi’s reign, as attackers around the world recorded video pledges of fealty to the caliph before carrying out killings.

Counterterrorism officials said to expect in the coming weeks a string of videos pledging allegiance from Islamic State affiliates in Afghanistan, Sinai, the Philippines and other far-flung insurgent hot spots.

“This will possibly be followed by a message from the new leader,” said Laith Alkouri of the business risk consulting company Flashpoint Global Partners, who monitors the group’s online messages. “He’s inherited the burden of leading the group and he needs to put on a show to maintain the morale of the support base.”

Clarke added, “This selection of the new leader is a way for ISIS to link its past with the future it will promise its adherents and followers.”

Intelligence officials and analysts were trying to make sense of the announcement and to place the announced successor among the known cadre of the Islamic State. Some speculated that Abu Ibrahim al-Hashemi may be a new nom de guerre of Hajji Abdullah, who appears in recently recovered internal Islamic State records archived by Aymenn al-Tamimi, a researcher.

“It could be to create confusion or for operational security reasons,” said Aaron Zelin, a fellow at the Washington Institute for Near East Policy.

The recent announcement by the State Department of a $5 million reward for information leading to his capture was a sign of the importance that the United States placed on him.

Besides the new leader, the Islamic State announcement also proclaimed a new spokesman, identified as Abu Hamza al-Qurayshi, again using a name indicating a lineage from the Prophet’s tribe, and setting up another potential successor.

“Those names are the most generic names I can think of in a long time,” Raineri said. “This trick is obfuscating on purpose the possible links to people we know.”