The Israeli Mossad assassinated Hamas political leader Ismail Haniyeh by detonating an explosive device planted in advance in his bedroom at the Iranian government official residence in Tehran, two sources with knowledge of the issue confirmed to Axios.

Why it matters: The fact that the Mossad managed to plant the explosive device in a high-security facility shows not only the deep penetration of Israeli intelligence services inside Iran but also the vulnerabilities of the Iranian intelligence and security apparatus.

• The details about the planted explosive device were first reported by the New York Times and confirmed to Axios by two sources.

Driving the news: The explosion that killed Haniyeh took place on Tuesday night, but the official announcement of his assassination was published several hours later on Wednesday morning.

• The initial statement from Hamas said Haniyeh was killed in an Israeli airstrike.
• Iranian media first reported three missiles were launched by a drone and later that the missile was launched from outside of Iran.

Behind the scenes: The sources said Israeli intelligence learned which facility — and which exact room — Haniyeh stayed in during his visits to Tehran.

• The bomb was planted in the room in advance, the sources said.
• They added that the bomb was a high-tech device that used artificial intelligence.
• It was detonated remotely by Mossad operatives who were on Iranian soil after receiving intelligence that Haniyeh was indeed in the room.
• The IRGC said it has opened an investigation around the incident.

Israel didn’t inform the U.S. or any other ally in advance of the assassination.

• But the sources said that on Wednesday evening Israeli officials briefed their U.S. counterparts about the details of the operation.

What they’re saying: Israel Defense Forces spokesperson Rear Adm. Daniel Hagari said in a press briefing on Thursday that there was no Israeli airstrike or missile attack anywhere in the Middle East on Tuesday night other than the one in Beirut.

• He claimed that in the last year Iran worked on smuggling sophisticated explosive devices to terrorist groups in the West Bank.

The big picture: Israeli Prime Minister Benjamin Netanyahu, who is directly in charge of the Mossad, made the decision to assassinate Haniyeh.

• The sources said the negotiations to reach a deal to release hostages held by Hamas in Gaza and establish a ceasefire were a consideration in the decision-making process.
• One of the sources said the Mossad position was that Haniyeh’s assassination would bring justice to the Oct. 7 attack victims and remove an obstacle to the hostage deal. The source claimed Haniyeh held a more hardline view on the deal than Hamas leader in Gaza Yahya Sinwar and was making it more difficult to get a deal.
• “Haniyeh presented a pragmatic face to the mediators but internally inside Hamas led a hard line,” the source said.