WASHINGTON (AP) — The seven World Central Kitchen aid workers killed by Israeli airstrikes represented the “best of humanity” and risked everything “to feed people they did not know and will never meet,” José Andrés, the celebrity chef who founded the organization, told mourners who gathered Thursday to honor the dead.

Speaking at Washington National Cathedral, Andrés said there was no excuse for the killings and he called for an investigation into the deaths. He appeared to struggle at times to maintain his composure, his words focused on the lives and contributions of the aid workers as he pleaded for greater compassion.

“The seven souls we mourn today were there so that hungry people could eat,” said Andrés, reading aloud their names. "Their examples should inspire us to do better, to be better.”

The workers were killed April 1 when munitions fired from Israeli armed drones ripped through vehicles in their convoy as they left one of World Central Kitchen’s warehouses: Palestinian Saifeddin Issam Ayad Abutaha; Britons John Chapman, James Kirby and James Henderson; dual U.S.-Canadian citizen Jacob Flickinger; Australian Lalzawmi Frankcom; and Polish citizen Damiam Sobol.

Hanging on the altar behind Andrés were flags of the slain humanitarian workers' home countries, alongside the red, green, black and white Palestinian flag. More than 500 mourners sat in pews below the cathedral's soaring stained glass windows.

Andrés spoke in depth about each one and their contributions to the work of feeding people suffering through disaster and deprivation — human-made and natural — around the world.

He said Chapman was “brave, selfless and strong” and had the ability to make people around him feel “loved and protected.”

Andrés said Flickinger was a problem-solver, “exactly what you need” in the chaos of a disaster zone and Frankcom gave “joy to others even more than she gave food."

He talked of how Henderson had taught first aid in Ukraine and was an avid rugby player. He said Kirby, known to friends as “Kirbs," was driven to help people in need. And he said a town in Turkey had named a street after Sobol, in honor of his work there after an earthquake.

Andrés noted that Abutaha's family was unable to attend the memorial, and he read from a message sent by the 25-year-old's brother that called the aid workers “heroes” and urged World Central Kitchen to continue its work in Gaza and across the globe, "carrying on the spirit of the fallen, and the resilience of the Palestinian people.”

At times, Andrés spoke emotionally about the organization's mission and why aid workers do what they do.

“We stand next to communities as they feed themselves, nourish themselves, heal themselves. People don’t want our pity. They want our respect. Our only way to show respect is facing the mayhem alongside them,” he said. “We remind them by showing up that they are not alone in the darkness.”

After an unusually swift Israeli investigation, Israel said the military officials involved in the attack had violated policy by acting based on a single grainy photo that one officer had contended — incorrectly — showed one of the seven workers was armed. The Israeli military dismissed two officers and reprimanded three others.

“I know we all have many unanswered questions about what happened and why. There is no excuse for these killings," Andrés told mourners, demanding an investigation. "The official explanation is not good enough.”

The aid workers, whose trip had been coordinated with Israeli officials, are among more than 220 humanitarian workers killed in the Israel-Hamas war that began Oct. 7, according to the United Nations. That includes at least 30 killed in the line of duty.

The international prominence and popularity of Andrés and his nonprofit work galvanized widespread outrage over the killings of the group’s workers. The deaths intensified demands from the administration and others that Israel’s military change how it operates in Hamas-controlled Gaza to spare aid workers and Palestinian civilians in the territory who are facing a humanitarian crisis and desperately need aid from relief organizations as the U.N. warns of looming famine.

World Central Kitchen, along with several other humanitarian aid agencies, temporarily suspended work in the territory after the attack. “We haven’t given up,” World Central Kitchen spokesperson Linda Roth said last week. “We are in funeral mode right now.”

Douglas Emhoff, husband of Vice President Kamala Harris, and Kurt Campbell, the deputy secretary of state, were among those at the event, joined by diplomats from more than 30 countries, along with representatives from the State Department and the U.S. Agency for International Development.

Democratic Sen. Chris Van Hollen of Maryland, one of the most active lawmakers pushing President Joe Biden to condition military aid on improved Israeli treatment of aid workers and Palestinian civilians, joined the mourners as a lone bagpiper played.

Biden sent a letter that was read privately to the families before the service, the White House said.