Mr. Trump later confirmed plans to visit Pittsburgh on Tuesday.

Rabbi Myers, who was hired just over a year ago by the Tree of Life congregation, which numbers a few hundred families, has found himself serving as a spiritual leader to an entire country in shock after the massacre, which left 11 people dead.

At a vigil in Pittsburgh and in a series of television interviews, the rabbi has warned that the attack was aimed at the American ideal of freedom of worship, and at America itself.

He has also reiterated his belief that good will prevail over evil.

He awoke on Monday to hundreds of emails from strangers, he told CNN, sent by people of all faiths and from all around the world. He has said the synagogue will not close down or cede any ground to violence. And he has called on politicians to avoid hateful rhetoric.

“My cup overflows with love,” Rabbi Myers said at the vigil in Pittsburgh on Sunday, according to an account in The Pittsburgh Post-Gazette. “That’s how you defeat hate.”

Rabbi Myers made the first 911 emergency call on Saturday morning when the gunman began his deadly assault. Until two months ago, he rarely carried his cellphone on the Sabbath, when some Jewish people avoid using technology and electronics, he has said in interviews. But at a training session in August, he said, a security expert told him he should start.