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More than a year after Hamas' devastating attacks on Israel on October 7, the country's military said on Thursday it had killed the man it believes was the main architect of that cross-border massacre – raising questions about the future of the war and the future of the war It is a militant group itself that has suffered one blow after another in recent months.

The death of Hamas leader Yahya Sinwar could represent a rare opportunity for a ceasefire, U.S. officials say – as Israel has killed several other senior Hamas commanders, including Ismail Haniyeh, the group's former political leader, as well as leader of the militant group Hezbollah in Lebanon.

Hamas and Hezbollah are both part of an axis of militant groups backed by Iran.

In a recorded video message on Thursday, Israeli Prime Minister Benjamin Netanyahu said Sinwar's death was “the beginning of the day after Hamas” but “the task ahead is not yet complete.”

Hamas has not yet commented on reports of its leader's death.

Here's what you need to know:

Since the Oct. 7 attacks, Israel has poured its resources into a fierce manhunt for Sinwar, declaring him the most wanted man in Gaza and a “dead man walking.” At one point, an Israeli military spokesman said the hunt “will not stop until he is captured, dead or alive.”

And U.S. officials believe the Israeli military came close a few times, even obtaining a video that purportedly showed Sinwar with several family members in a Gaza tunnel — but he kept slipping away. Previously, the Israeli military had surrounded Sinwar's home and carried out an intensive attack on his hometown of Khan Younis, but was unable to find him.

This year-long search finally came to an unexpected end on Wednesday in Rafah, southern Gaza. Israeli forces were in the area during a routine military operation when they came under fire near a building, according to two Israeli sources familiar with the matter.

According to the Israeli military, troops returned fire with a tank and then flew a drone into the heavily damaged building. Video shared by the military shows Sinwar's apparent final moments: he sits alone in a chair, surrounded by dust and debris, and appears to look directly into the camera. He holds a piece of wood and throws it at the drone before the video ends.

Only then and when troops inspected the rubble did they discover that Sinwar was among the bodies, according to the Israeli military.

Dental records and other biometric data helped Israel identify the Hamas leader, according to a U.S. official and former official familiar with the matter.

Sinwar was trying to flee to the north when he was killed, another Israeli military spokesman said Thursday. He was found with a gun and more than 10,000 Israeli shekels, the spokesman said.

Sinwar has long been a key player in Hamas, joining the militant group in the late 1980s and quickly rising through the ranks.

He was born in a refugee camp in Gaza after his family was expelled from the Palestinian village of Al-Majdal – now part of the Israeli city of Ashkelon – during the Arab-Israeli war.

As a student, Sinwar became an anti-occupation activist but was sentenced to multiple life sentences in Israel after being accused of orchestrating a murder. He served 23 years in prison before being released in a prisoner exchange in 2011.

Sinwar returned to Gaza and quickly made a name for himself within Hamas. He founded the group's feared international intelligence arm, the Majd, and was known for using brutal force against anyone suspected of collaborating with Israel.

Some also viewed him as a pragmatic political leader: in 2017, Hamas elected Sinwar as political chief of the Politburo, its main decision-making body in Gaza.

Sinwar was designated a global terrorist by the U.S. State Department and the European Union in 2015 and has been sanctioned by the United Kingdom and France in recent years.

But after the October 7 attacks, he gained greater prominence as one of Israel's main targets. Israeli officials called him the “face of evil” and “the butcher of Khan Younis.”

He became one of Hamas's most senior leaders in August after the assassination of Ismail Haniyeh in Iran. Sinwar had not been seen since the October 7 attacks and likely survived Israel's siege of Gaza by bunkering down in a vast network of underground tunnels.

Israel has publicly accused Sinwar of being the “mastermind” behind Hamas' October 7 attack – although experts say he was likely one of several.

The attack was the deadliest attack on Israel in its history. Hamas and other Palestinian armed groups killed more than 1,200 people, mostly civilians, and took about 250 people hostage in Gaza.

Sinwar was considered a key decision-maker and probably the most important contact for the outside world in Gaza during the intensive negotiations over the return of the hostages.

Senior figures from Israel, Hamas, the United States, Qatar and Egypt took part in the talks.

While it is still too early to say what might happen next or how Hamas might respond, Sinwar's killing marks the latest blow to the group – which has killed several top leaders one by one during Israel's campaign to completely dismantle Hamas has.

Just a day after Haniyeh's killing, Israel confirmed that it had killed Hamas military chief Mohammed Deif – another of the suspected masterminds of the October 7 attack – in an earlier attack.

With a ceasefire and hostage release agreement to end the war stubbornly stalled for months, senior U.S. officials had clung to hope that Sinwar could one day be defeated – paving the way to a resolution. With him now gone, officials speculate that this could be one of the best chances to end the war between Israel and Hamas, but are cautious about predicting what it will ultimately mean for the volatile region.

US President Joe Biden spoke to Netanyahu in a phone call on Thursday in which “both leaders agreed that there was an opportunity to move forward with the release of the hostages and that they would work together to achieve this goal.” said a reading from the Prime Minister's Office.

But much remains unknown – including the fate of Sinwar's brother.

Mohammed Sinwar recently took over as Hamas' military commander, a senior Israeli official told CNN last month. The brothers were very close and were often still together until late August, the same official told CNN.

If Mohammed survives this week, he will likely continue his brother's tough negotiating tactics as Israel tries to free its remaining hostages from the Palestinian enclave. But until a clear picture emerges, it will be difficult to see the militant group's next move.

And even after Sinwar's death, the broader Middle East conflict continues to rage – particularly as Israel prepares to retaliate against Iran's ballistic missile attack earlier this month. CNN previously reported that this move was expected before the US election.

And beyond the Israeli-Lebanese border, another front of the conflict is emerging: Hezbollah announced on Thursday a “new and escalating phase” in its war with Israel.

Hezbollah has also suffered significant losses in recent months – from the deadly pager and walkie-talkie attacks that killed dozens and injured thousands, many of them civilians, to the assassinations of several senior commanders, including its boss Hassan Nasrallah last month.

Meanwhile, Palestinians in Gaza told CNN they do not believe Sinwar's killing will end the war – although some expressed tentative hopes.

“Sinwar died, but so many of our people were killed and there is now no excuse for Netanyahu to continue the war,” said 22-year-old Mumen Khalili.