JERUSALEM — From across the interrogation table in an Israeli jail Yahya Sinwar coldly recounted gruesome details of his murders.

The year was 1989. The future Hamas leader, then the group’s internal enforcer, would be convicted of killing four fellow Palestinians.

He described making a Hamas member call his brother — a suspected collaborator — to arrange a meetup, recalled Michael Koubi, who spent more than 150 hours questioning him for Shin Bet, Israel’s domestic intelligence agency. Sinwar made the fighter bury his brother alive.

He showed “no emotion at all,” said Koubi. “I saw a man that was very clever … and he really believed in everything he did.”

The details of the 61-year-old’s ruthless tactics as a young man when he headed the Majd, Hamas’ internal security force, shed light on the leader he would become — dedicated to the destruction of Israel and accused of masterminding the Oct. 7 attack on the country’s south, where militants killed 1,200 people and abducted nearly 250 others.

Now, he is at the top of Israel’s hit list in Gaza, thought to be hiding in its vast underground tunnel network as Israeli forces scour the tiny enclave and pummel it with airstrikes. The war has killed more than 18,000 Palestinians in just two months, according to Gaza’s Health Ministry, and it is unlikely to end until Sinwar is dead or captured.

Interrogation transcripts and the accounts of Israeli security officials, fellow prisoners and others who have met him point to an uncompromising strategist with a penchant for close quarter killing, shaped by a harsh upbringing in a Palestinian refugee camp and decades in Israeli detention. He spent his 22 years in jail closely studying his enemy, pouring over books on Israeli politics and learning fluent Hebrew.

To understand Sinwar, one must first understand where he came from, said his former prison mate Esmat Mansour.

“He said his family lived in tragedy,” Mansour recalled. “He said these memories wouldn’t leave him.”

Sinwar was born in Gaza’s Khan Younis refugee camp in 1962. His family was forced out of the Palestinian town of Madjal in the wake of Israel’s 1948 war for independence, a period known to Arabs as the Nakba, or “catastrophe,” when hundreds of thousands of Palestinians were displaced.

After Madjal was emptied of its Palestinian population — the last residents were deported in 1950 — Israel renamed the city Ashkelon. Sinwar would later spend time in jail there.

By the time he was born, the refugee tents among the sand dunes at Khan Younis had been replaced by small cinder block houses, but conditions were still dire.

Sinwar talked about the lack of sanitation and the struggle to live on U.N. handouts, said Mansour.

“He’d always go back to these stories when he’d tell us to struggle against the occupation,” said Mansour. Sinwar fiercely opposed the 1993 Oslo accords, the U.S.-brokered agreement that outlined a two-state solution to the conflict.

“He was a radical,” Mansour said. “He wanted to fight back.”

He was first arrested by Israel in 1982 as a university student at the Islamic University in Gaza, where he was a founding member of Hamas’ student movement, said Ibrahim al-Madhoun, a Hamas-affiliated columnist. He described Sinwar as “unwavering in his decisions, even if they are harsh.”

Sinwar was active during the first intifada, or uprising against Israel, which began in Gaza in 1987. He became close to Hamas’ founder Sheikh Ahmed Yassin, praying at the same mosque with him in Gaza City.

He was detained again in 1988 after being injured when an improvised explosive device he was making went off, said Koubi. It was only in jail that his role in the killing of Gazans suspected of collaborating with Israel emerged.

“The first day, he was very tough, he didn’t want to say anything,” said Koubi, adding that he eventually confessed to 12 killings, but was only convicted on four counts.

While Israel is notorious for its harsh interrogation techniques, Koubi said Sinwar was not physically abused. It was not possible to verify his claims.

In a 10-page transcript from his interrogation held at Israel’s Supreme Court and later published by Israeli media, Sinwar described strangling victims to death. Koubi said he also liked to use a machete; some Gazans nicknamed him the “Butcher of Khan Younis.”

He describes killing one suspected collaborator in an open grave in the local cemetery. “I tied his eyes with a rag so he couldn’t see, put him in a large grave I saw, and suffocated him with a rag,” the transcript reads, according to excerpts published by Israel Hayom. “After strangling him, I wrapped him in a white cloth and closed the grave.”

Koubi said he was not surprised by the brutality of the Oct. 7 attack: “He has very deep hate.”

Sinwar quickly rose through the ranks of Hamas after being released from jail in 2011 along with 1,026 other Palestinian prisoners in exchange for kidnapped Israeli soldier Gilad Shalit. But it was in prison that he built his influence.

“He didn’t come from nowhere,” said Mkhaimar Abu Sada, a professor in politics at Gaza’s Al Azhar University.

At first he held little clout in the Israeli penal system, where prisoners are divided into various Palestinian factions. But even on the inside, he continued to hunt for collaborators with Israel, Mansour and Koubi said.

As Hamas grew more prominent in the Palestinian political scene, Sinwar’s star began to rise.

Around the time of the second intifada, he was elected Hamas’ leader in the prison, where he led strikes in an effort to improve conditions for inmates.

In June 2006, Sinwar’s younger brother, Muhammad Sinwar, was suspected of playing a key role in the cross-border raid that led to Shalit’s capture.

“When Hamas got stronger, and they kidnapped Shalit, he became the one man show,” said Mansour.

He was no longer interested in meeting with prison authorities, Mansour said, instead holding court with Israeli intelligence and other officials seeking Shalit’s release.

When Sinwar was released, he addressed cheering crowds in Gaza City, calling on Hamas to free those remaining in Israeli jails. “This must turn immediately into a practical plan,” he said. He remains deeply invested in the plight of Palestinian prisoners, according to those who know him, which likely helped drive the mass kidnappings of Israelis on Oct. 7.

In public interviews before the attack — including one with an Israeli newspaper in 2018 — he said he was not seeking confrontation. “I don’t want any more wars,” he told Yedioth Ahronoth, an Israeli newspaper. But other comments were more extreme, said Abu Sada, the university professor, pointing to a call by Sinwar last year for Palestinians to carry out lone wolf attacks with cleavers, axes and knives.

By joining the political wing of Hamas, he effectively blurred the distinction between the group’s fighters and officials, said Shlomi Eldar, an Israeli journalist who authored a 2012 book on Hamas and interviewed some of its most senior officials.

“He changed the movement,” said Eldar. None of the group’s other leaders would have orchestrated an attack on the scale of Oct. 7, he said, fearing the backlash. But Sinwar is different: “The only explanation I can give is that it’s his personality.”

In his gamble, others suspect he was trying to position himself as the leader of the Palestinian cause, a role he had long sought. “I felt like he was saying, ‘I am Yasser Arafat 2,’ ” said one Palestinian official who met Sinwar several times.

“No one can deny that he recorded his name in history on the one hand and changed the static situation that Israel adopted to deal with the Palestinians,” the official said, speaking on the condition of anonymity to discuss the sensitive meetings.

Israel says Sinwar is a “dead man walking,” and it is only a matter of time before their forces catch up with him.

As the manhunt intensifies, the Hamas leader is likely surrounded by an inner circle of confidants — including his brother Mohammed, who faked his death in 2014 but has since reemerged.

“He will fight until the end,” said Koubi.

Balousha reported from Amman.

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