Hamas leader Yahya Sinwar killed in Gaza by Israeli forces, officials say

Hamas leader Yahya Sinwar was killed by Israeli forces in the Gaza Strip, Israel Foreign Minister Israel Katz said Thursday.

Sinwar has been credited as the mastermind behind the Oct. 7, 2023, attack on Israel that led to the deaths of 1,200 people, the worst terrorist attack in Israel's history.

"The master murderer Yahya Sinwar, who is responsible for the massacre and atrocities of October 7, was killed" by Israel Defense Forces soldiers, Katz said in a statement. "This is a great military and moral achievement for Israel and a victory for the entire free world against the evil axis of extreme Islam led by Iran."

Sinwar, 62, had served as Hamas' leader in Gaza since 2017 and assumed leadership of the group's political bureau after the assassination of Ismail Haniyeh in Iran this July.

Israeli authorities said they had been pursuing Sinwar for a year and that he had been hiding "behind the civilian population of Gaza, both above and below ground in Hamas tunnels in the Gaza Strip." The IDF and Israel Security Agency said their operations in recent weeks in southern Gaza restricted his movement and "led to his elimination" on Wednesday.

The killing of Sinwar happened by chance, according to an official with knowledge?of the operation.

A unit of reserve combat soldiers in Rafah attempting to blow up a missile that failed to explode fired upon a group of four armed men, according to the official. They also fired upon a fifth person who was throwing grenades out the window of a nearby building at the soldiers, according to the official. The soldiers directed tank fire and a missile at the building, though the man was still alive, the official said. A sniper in the unit then fired upon him, the official said.

The IDF on Thursday released drone footage they said shows Sinwar in the building, wounded in the shooting.

When a different unit went to check to see if the man was still alive Thursday morning, they discovered the body of Sinwar, the official said.

"Sinwar died while beaten, persecuted and on the run -- he didn't die as a commander, but as someone who only cared for himself," Israeli Minister of Defense Yoav Gallant said in a statement. "This is a clear message to all of our enemies – the IDF will reach anyone who attempts to harm the citizens of Israel or our security forces, and we will bring you to justice."

The IDF initially said they were "checking the possibility" that the Hamas leader was among three militants killed in an operation in Gaza and were working to confirm identification through dental images and DNA testing.

Israeli police later said there was a "definitive identification" of Sinwar's assassination based on a comparison of dental records and fingerprint matching.

Israeli Prime Minister Benjamin Netanyahu heralded his death as "an important landmark in the decline of the evil rule of Hamas" in a video address.

Katz said Sinwar's death "creates a possibility for the immediate release of the abductees and to bring about a change that will lead to a new reality in Gaza -- without Hamas and without Iranian control."

Israeli President Isaac Herzog also said in a statement that Israel "must act in every way possible to bring back the 101 hostages" still in Gaza.

Netanyahu said that to those who peacefully return the hostages, "we will allow him to go out and live."

"The return of our hostages is an opportunity to achieve all our goals and it brings the end of the war closer," he said.

President Joe Biden said in a statement that he directed Special Operations personnel?and intelligence professionals to "work side-by-side with their Israeli counterparts to help locate and track Sinwar" and other Hamas leaders hiding in Gaza.

"There has rarely been a military campaign like this, with Hamas leaders living and moving through hundreds of miles of tunnels, organized in multiple stories underground, determined to protect themselves with no care for the civilians suffering above ground," he said. "Today, however, proves once again that no terrorists anywhere in the world can escape justice, no matter how long it takes."

Biden said it is a "good day" for Israel, the U.S. and the world, and likened Israelis' reactions to the death to "scenes witnessed throughout the United States after President Obama ordered the raid to kill Osama Bin Laden in 2011."

During remarks upon landing in Berlin on Thursday, Biden told reporters that he spoke to Netanyahu to congratulate him and said they will "work out" the day-after plan. He added that it was "time for this war to end and bring these hostages home."

Seven Americans are among the 101 hostages remaining in Gaza, four of whom are believed to still be alive, Biden said.

During remarks while at a campaign stop in Milwaukee, Vice President Kamala Harris said Sinwar has "blood on his hands" and assured that "any terrorist who kills Americans, threatens the American people or threatens our troops or our interests, know this, we will always bring you to justice."

After Israeli forces and officials announced the death of the Hamas leader, the Lebanese militant group Hezbollah said Thursday they are transitioning into a "new, escalated phase" in the "confrontation with the Israeli enemy."

This new phase in the conflict "will be revealed by the developments and events in the coming days," Hezbollah said in the statement.

In 1989, an Israeli court sentenced Sinwar to four life sentences for his role in killing suspected Palestinian informers and plotting to murder two Israeli soldiers.

Sinwar spent the following 22 years in prison before becoming one of more than 1,000 Palestinian detainees released in 2011 in exchange for Israeli soldier Gilad Shalit, who had been held hostage by Hamas for five years.

ABC News' Guy Davies, Matt Gutman and Jordana Miller contributed to this report.