Nearly every week for a decade, Iri Kassel picked up sick Palestinian children at Israel’s Erez border crossing with Gaza and drove them with their guardians to Israeli hospitals for treatment.

But on Oct. 7, the crossing was raided by Palestinian militants who blasted the passport control booths and magnetic scanners as they stormed into southern Israel.

The deadly attacks plunged Israel into all-out war in Gaza and disrupted the work of Road to Recovery, the Israeli nonprofit organization that Mr. Kassel volunteers for, which has ferried more than 1,500 Palestinian patients a year to Israeli hospitals.

Several of the group’s volunteers died in the Hamas-led attack, including Vivian Silver, a prominent peace activist who was killed in her home at Kibbutz Be’eri in southern Israel. Others were taken hostage, like Oded and Yocheved Lifshitz, a couple in their eighties from Nir Oz, a kibbutz near the Gaza border. Dozens more lost loved ones or were evacuated from their homes near Gaza.

The organization’s staff and volunteer drivers were devastated. “It was a blow to the stomach,” Mr. Kassel said. Even for those who survived the attacks, he said, there was “an almost physical pain.”

Road to Recovery was founded in 2010 by Yuval Roth, a peace activist whose brother had been kidnapped and killed nearly 20 years earlier by Hamas militants. The group helps Palestinians from Gaza and the West Bank access medical treatment in Israel, where health services are among the most advanced in the region.