A specialist in family and emergency medicine, Morel was told by phone that an attack was underway.
"I got the call, and I ran," she told the Israeli newspaper Haaretz.
Canada and the U.S. were among countries that quickly condemned the attack Tuesday that involved two cousins, who stormed the synagogue, and attacked worshippers with meat cleavers and a gun during morning prayers before they were shot dead by police.
Morel is described by Haaretz as an ultra-Orthodox physician who lives in the HarNof area of the city. She works with United Hatzalah, an Israeli volunteer emergency medical service.
"It was extremely upsetting to see seriously injured people just near a shul [synagogue] like that," she told Haaretz.
As she began to treat a man with head injuries outside the synagogue, Morel said she could hear shooting inside.