At a sprawling cemetery in Jerusalem on Monday, thousands of people thronged the parking lot to memorialize Hersh Goldberg-Polin, a dual Israeli American citizen and one of six hostages whose bodies were found in Gaza on Saturday, as family members and friends delivered emotional eulogies and sang Jewish hymns.

The funeral, which was attended by President Isaac Herzog of Israel, was a somber reminder of the perilous situation facing the dozens of hostages still thought to be alive in the war-ravaged Gaza Strip. It reflected the resonance that Mr. Goldberg-Polin’s plight had with a wide spectrum of Israeli society, drawing secular and religious people who had never met him but found inspiration in his story.

The gathering also signified the end of a nearly 11-month journey, in which Mr. Goldberg-Polin’s parents, Jon Polin and Rachel Goldberg-Polin, crisscrossed the globe to lobby for their son’s freedom, meeting with President Biden, United Nations Secretary General Antonio Guterres and Pope Francis.

Clad in a ripped shirt, a Jewish mourning custom, Ms. Goldberg-Polin said it was a “stunning honor” to be her son’s mother and spoke of the unimaginable distress and torment of worrying about him.

“I tried hard to suppress the missing you part because that, I was convinced, would break me,” she said, describing the almost yearlong experience as an “odyssey of torture.”

Holding back tears, she expressed some relief that her son was no longer in danger.

“Finally, my sweet boy,” she said. “Finally, finally, finally, you’re free.”

Mr. Goldberg-Polin, born in the Bay Area before moving to Israel around 7, was abducted on Oct. 7 near the grounds of the Nova music festival, where he was celebrating his 23rd birthday. He was grievously injured that day and was seen in a video clip being forced to climb onto the back of a pickup truck with his left arm blown off.

Israeli forces discovered his body in a tunnel underneath the city of Rafah. Israel said Hamas had killed him; Israel’s health ministry said a forensic examination showed the hostages had been shot at close range sometime between Thursday and Friday morning

About the same time he was being kidnapped, Ms. Goldberg-Polin found two texts from her child. “I love you guys,” he had written his family. “I’m sorry.”

“Are you OK?” Ms. Goldberg-Polin wrote back. “Please let us know you’re OK.” There was no reply.

President Herzog, whose position is largely ceremonial, expressed remorse that Israel had failed both to protect Mr. Goldberg-Polin on Oct. 7 and to bring him home alive.

“I ask for forgiveness in the name of the state of Israel,” he said. “I apologize that the country you immigrated to at the age of 7, wrapped in the Israeli flag, could not keep you safe.”

In comments seemingly directed at Prime Minister Benjamin Netanyahu of Israel, Mr. Herzog demanded that the country’s leaders take action to secure the freedom of the remaining hostages in Gaza.

“Decision makers must do everything possible, with determination and courage, to save those who can still be saved and to bring back all our sons and daughters, our brothers and sisters,” he said. “This is not a political goal, and it must not become a political dispute. It is a supreme moral, Jewish and human duty of the state of Israel to its citizens.”

Other notable people who attended the funeral included Jacob J. Lew, the United States ambassador to Israel, who appeared shaken as he watched Mr. Goldberg-Polin’s burial; and Eli Groner, the former director general of the Israeli prime minister’s office.

Mr. Polin said his son had challenged him and his other family members to think hard about a wide array of issues, including the ethics of eating animals and Israeli settlement policy.

He was “always seeking to understand the other,” he said.

In his bedroom, Mr. Goldberg-Polin had kept a rectangular piece of artwork that read “JERUSALEM IS EVERYONE’S” in English, Hebrew and Arabic.

Yaniv Mezuman, 48, a former teacher, said Mr. Goldberg-Polin was a “special soul” who showed incredible intellectual curiosity.

“He projected light on everyone he met,” he said. “I fell in love with him within a second of meeting him.”

Isabel Kershner contributed reporting to this article.