Who was Yahya Sinwar, the mastermind of Hamas' Oct. 7 massacre?

Israel eliminated Yahya Sinwar Thursday, the leader of the Hamas terrorist organization in the Gaza Strip and who orchestrated and directed the Oct. 7 massacre, in which roughly 1,200 people were killed and more than 250 were kidnapped.

Sinwar, 62, was born in Khan Younis and in the mid-1980s joined Hamas, where he founded Majed, the terrorist group's security arm, along with other members of the organization.

Sinwar was greatly influenced by Ahmed Yassin, the founder and leader of Hamas who was eliminated by Israel in 2004.

As one of Majed's referents, he created a mechanism to identify and execute Palestinians accused of collaborating with Israel, and in fact killed 10 of them himself.

Sinwar was nicknamed the "Butcher of Khan Younis" because of the cruelty with which he treated the Palestinians themselves, including the group's opponents and those accused of collaborating with Israel.

In 1989, he was convicted of murdering four Palestinians who were accused of collaborating with Israel and was sentenced to five life sentences in the Jewish state.

While imprisoned in Israel, Sinwar learned Hebrew, a language he can speak fluently, studied the society of the Jewish state in depth and had a brain tumor operation performed by an Israeli doctor that saved his life in 2008.

After repeated unsuccessful attempts to escape from prison, Sinwar was released in 2011 with about 1,000 other terrorists in exchange for Israeli soldier Gilad Shalit, who had been kidnapped by Hamas five years earlier.

In a speech after his release, Sinwar called for the continued kidnapping of Israelis to free the remaining terrorists imprisoned in Israel.

Sinwar was elected as Hamas' leader in Gaza in 2017. A year later, he organized a series of violent protests against Israeli soldiers on the border between the Gaza Strip and Israel.

After Oct. 7, 2023, Sinwar hid in Hamas' tunnels in Gaza, allegedly surrounded by hostages to use them as human shields, and was in charge of indirect negotiations with Israel to exchange Israeli hostages for Palestinian terrorists.

Sinwar was chosen to replace Ismail Haniyeh, leader of Hamas' political bureau, after he was eliminated in Tehran, Iran, in an operation attributed to Israel in late July.