Yehudit Weiss, 65, was one of some 240 hostages snatched by militants and taken to the Gaza Strip, according to Israeli authorities.
With their home in kibbutz Beeri devastated in the attack, Weiss and his wife and baby daughter have been staying with friends in the coastal city of Netanya.
"The officers knocked on the door and we immediately understood," he told AFP, his eyes filled with tears.
"They handed us the notice and the world collapsed for the second time."
It was not his first such door knock: barely five weeks earlier, authorities had come to tell him his father Shmulik was dead.
For the past six weeks, Israel has been waging a deadly war in Gaza to wipe out the Palestinian territory's Hamas rulers and bring home the hostages, among them a baby, dozens of children, scores of women and a number of people in their 80s.
But on Thursday evening, the army said it had found the body of Yehudit Weiss near Al-Shifa hospital in Gaza City, saying she had been killed by militants.
The kibbutz she called home lies just four kilometres (2.5 miles) from the Gaza border and was devastated by the attack, with 85 residents killed and another 30 kidnapped and taken to Gaza, or listed as missing.
During the October 7 attacks, the deadliest in Israel's history, militants killed some 1,200 people, mostly civilians, according to Israeli officials.
Israel is hitting back with a deadly campaign that has claimed at least 12,000 lives, also mostly civilians and including thousands of children, according to Gaza's Hamas-run health ministry.
'We were lucky'
On the day of the massacre, Weiss -- who works at the kibbutz's printing firm -- said he and his family survived because the militants simply did not come to their house.
It was, he said, like a game of "Russian roulette, my parents had bad luck and we were lucky."
He and his wife, who also have a two-year-old, pushed their way onto a crowded bus and escaped. But he remains haunted by the images he saw as they fled.
"Burnt-out cars with bodies inside, and a lot of bodies scattered on the road," he told AFP, saying the bus even drove over some of the remains.
"It was the only way to get out."
After hearing about the death of his father, a 65-year-old mechanic, Weiss and his siblings clung onto the hope that they would see their mother again.
"We still had the hope Mum would come back and that we could mourn him together," he said.
But since October 7, he and the other families of hostages taken to Gaza heard nothing. "We endured 40 days with not even a grain of information about Mum," he said.
The funeral for his mother, a former nurse, will take place on Sunday near Netanya where she will be laid to rest alongside his father in a temporary grave.
And one day, he hopes to be able to rebury them both side by side in Beeri if their kibbutz is ever rebuilt.
Before then, he is hoping many of the hostages can still be saved.
"Our hearts are with the families of the kidnapped," he said.
"We sought help from the Red Cross, from Doctors Without Borders, from human rights organisations," he said, describing how the families had written to the army, to the Israeli government and to representatives of the European Union and the United States.
"Nobody answered us."
