The Hamas leader was in Tehran for a welcoming ceremony to the new President, Masoud Pezeshkian.
Iran's previous president, Ebrahim Raisi, died in a mysterious helicopter crash in Azerbaijan which most blame on Israel.

https://www.presstv.ir/Detail/2024/0...Ismail-Haniyeh

‘They killed peace, not Ismail Haniyeh’

War-weary Palestinians in Gaza are mourning the killing of Hamas political leader Ismail Haniyeh.
“This man could have signed the prisoner exchange deal with the Israelis,” said Saleh al-Shannar, who was displaced from his home in northern Gaza. “Why did they kill him? They killed peace, not Ismail Haniyeh.”
Nour Abu Salam, a displaced woman, said the killing shows Israel doesn’t want to end the war and establish peace in the region.
“By assassinating Haniyeh, they are destroying everything,” she said.

https://www.aljazeera.com/news/liveb...tion-operation

“We consider his revenge as our duty,” Iranian supreme leader Ayatollah Ali Khamenei said in a statement on his official website. He said Israel had “prepared a harsh punishment for itself” by killing "a dear guest in our home."

https://abcnews.go.com/International...hran-112427534