AMNA NAWAZ: Today, Israel marked one of its darkest days in history.

October 7, the third anniversary of Hamas terrorists storming Israeli communities, killing 1,200 people, kidnapping 251 more, and sparking multiple wars that still shake the region.

Our coverage begins with one survivor and his determination to create out of the horrors a new generation of Israeli leadership.

And a warning that the story includes disturbing images.

NICK SCHIFRIN: Tonight in Tel Aviv, a moment of silence for the moment that changed a nation, tens of thousands of Israelis remembering those killed, grieving a day that divides history.

Omri Shifroni has done this before.

This is the third national rally he's helped organize, but the first since all Israeli hostages were released or their bodies returned from Gaza.

That gives him hope that, out of a dark past, there's a brighter future.

OMRI SHIFRONI, Kumu Movement: For the people of Israel and bereaved families to rise up from the dust, from the ashes, and to build a new leadership and new Israel society from the memory, from the memory of October 7.

NICK SCHIFRIN: Three years ago, Shifroni and Kibbutz Be'eri, less than two miles from the Gaza border, woke up to horror.

More than 340 gunmen, some wearing Israeli military uniforms, invaded Be'eri's three square miles.

OMRI SHIFRONI: It was 6:30 a.m.

It starts to -- the shooting, the bombs.

My brother, a Hamas terrorist just burn his house.

NICK SCHIFRIN: They shot and killed civilians point blank, dead bodies discarded or denied dignity and taken back to Gaza.

A couple embracing each other were burned alive.

In total, 30 residents were kidnapped and 101 killed, including Shifroni's niece and nephew, 12-year-old twins Liel and Yannai, seen here celebrating their birthday six months before they were murdered.

Also killed at Be'eri that day, Aviya and Ayala Hetzroni, his uncle and aunt.

OMRI SHIFRONI: I lost part of my family in Be'eri, four members of my family, my uncle, my aunt.

I have four friends was in captivity, one of them murdered in captivity.

NICK SCHIFRIN: In Be'eri and other devastated communities today, it is hard to heal, perhaps even harder to rebuild trust, because the terror also broke Israelis' faith in their government.

Be'eri felt abandoned, as I learned on the first anniversary of October the 7th.

The IDF's own investigation into actions here in Be'eri admitted that it failed the residents here, that the early response was characterized by a lack of coordination and command and control, and that the residents of Be'eri were largely left on their own for the first seven hours.

OMRI SHIFRONI: It was seven hours when we were in Be'eri without an army inside the kibbutz.

And, afterwards, it was another seven hours of being alone until the army came to our place to rescue us and to evacuate us from Be'eri.

NICK SCHIFRIN: This week, during a memorial service, Prime Minister Benjamin Netanyahu was interrupted by a father whose son was killed on October the 7th.

He yelled: "You didn't protect my son.

Shame," he yelled, "disgrace."

Netanyahu has blamed security services for failing to prevent the attacks.

Netanyahu's critics blame him and argue he has never been held accountable and that he was reportedly repeatedly warned of an imminent attack.

And so, as Be'eri and many other communities today grasp their grief, they also envision a different future in a new generation of leaders.

Shifroni helped start the Kumu Movement, which demands accountability, works to restore public trust in the government, and tries to build a more just society.

OMRI SHIFRONI (through translator): We too will never be who we once were.

But we can choose to be better and more worthy.

From here, we rise.

From here, we mend.

From here, we rebuild.

NICK SCHIFRIN: Rebuilding with the faith that from tragedy can come renewal.