A barrel bomb crashed into the entrance of the rebel-held Syrian hospital, inundating the poorly ventilated, bustling medical facility with a poisonous gas that reeked of chlorine.

The toxic mixture penetrated all the way down to the basement-level operating rooms, where orthopedic surgeon Ali Darwish was in the middle of surgery.

While doctors, nurses and able-bodied patients fled for safety, Darwish refused to abandon his patient.

“He didn’t want to just leave and risk the life of the patient,” said Dr. Basel Termanini, 57, an Aleppo native who lives in Moon and coordinates humanitarian responses to Syrian President Bashar al-Assad regime’s attacks as vice president of the Syrian American Medical Society (SAMS).

Watch full interview here