AMNA NAWAZ: It was nearly three weeks ago that Hamas attacked Southern Israel with ferocious terror, killing more than 1,400 people.

Now, as Israelis mourn their dead, many are still trying to find their loved ones.

The task is monumental, painstaking, and often horrific.

Leila Molana-Allen reports.

And a warning: Images and accounts in this story are disturbing.

LEILA MOLANA-ALLEN: Along Israel's Gaza border, nearly three weeks after Hamas' terror attacks, there is still more horror to clear.

Soldiers secure the area against rockets and militants still infiltrating the border fence, but the most brutal of tasks now falls to hundreds of civilian volunteers, sorting through human remains; 56-year-old Eli moved to Israel from Rhode Island as a kid.

In peacetime, he is a carpenter.

ELI HAZEN, Volunteer: We are going after everything else through the houses in order to collect all the remnants.

Where we know the person was identified in this particular house, we put everything into a bag, and buried with him.

Other places we don't know, it is just buried in a mass grave.

LEILA MOLANA-ALLEN: Inside every shattered home in these small farming communities is another story of barbarous cruelty; 92-year-old Holocaust survivor Moshe (ph) was sleeping in his room when the kibbutz was attacked.

Militants fired the RPG at point-blank range through his armored window and then sent in two hand grenades afterwards to make sure he was dead.

In the living room, a lovingly made collage for grandpa.

Outside, volunteers have spent today collecting Moshe's remains from his shrapnel-ridden mattress.

The team isn't only trying to identify victims, but to lay their remains to rest.

By Jewish tradition, every part of the body must be buried.

Two young parents and their son were killed by grenades in this room of their house.

ELI HAZEN: They're working with paint scrapers, scraping off specks of paint and body - - skin or residue from the ceiling.

LEILA MOLANA-ALLEN: But many houses, cars and bodies were set aflame, leaving them burned beyond recognition.

On this army base in Tel Aviv, dozens of combat and civilian specialists, morticians, doctors, dentists among them, have come together to set up this mobile morgue and field forensics unit.

This facility had to be brought together as fast as possible to deal with the sheer scale of death from these terror attacks, behind me, cargo containers hastily formed into fridges to store the hundreds of bodies waiting to be identified and returned to their families.

Gilad Barat runs the operation.

Every day, truckloads more bodies arrive.

GILAD BARAT, Chief Superintendent, Head of Investigations: I have seen babies 6 years old, 2 years old that were -- was burned alive.

We had a truck the other day of I don't know how many, but small bags with children that each one of them was burned alive, mothers, mother hugging their child, trying to protect them.

And after they shot them and killed them, they abused the bodies with shovels, with axes.

They cut their heads, their hands.

We have many bags that contains body parts here.

We don't know if it's part of bodies that we already have here that are missing parts, or it's new bodies.

We don't know.

LEILA MOLANA-ALLEN: In a private screening with the Israeli military of footage from Hamas' body cameras, CCTV and victims' phones found at the scene, the "NewsHour" witnessed a record of the horrors of October 7, grenades thrown directly at families, a man being decapitated with a shovel from his garden, the tiny burned bodies of babies.

The shadow behind Gilad's eyes shows he has seen much more.

GILAD BARAT: The problem is that part of the bodies did not survive.

We cannot take fingerprints.

We cannot take DNA from them.

LEILA MOLANA-ALLEN: More than 1,400 people are confirmed dead; 222 are known to be held hostage in Gaza.

For the families of those still missing, their fates unknown, the weight is agony.

Esther Yahalomi is a grandmother to her core, plastered on the wall outside her bedroom pictures of her grandkids, so they're the last thing she sees at night and the first she sees in the morning.

That terrible morning, when Hamas militants entered her son Ohad's home, they shot him in the leg and kidnapped him, along with his wife, Batsheva, their 12-year-old son, Eitan, and their two daughters.

Batsheva and the girls managed to escape through the fields.

Eitan and Ohad have not been heard from since.

ESTHER YAHALOMI (Mother and Grandmother of Missing Victims): On one hand, I pray they're OK, and, on the other hand, I'm afraid to know.

But the not knowing is killing me.

LEILA MOLANA-ALLEN: Esther can't stand feeling so powerless, relatively safe here, when she can't do the same for her loved ones.

ESTHER YAHALOMI (through translator): I wake up in the morning and I ask myself, did he eat?

Did they give him clothes to wear?

He was just in his pajama shirt.

Are they beating him?

We don't know anything.

It's terrible.

During the days, I can hold myself together.

I don't want anybody to see me falling in my spirit.

But the nights, I'm torn between hope and fear.

LEILA MOLANA-ALLEN: And so she waits, hoping for good news, but preparing herself for the very worst.

Like so many here, her nightmare is far from over.

For the "PBS NewsHour," I'm Leila Molana-Allen in Rishon LeZion, Israel.