US Senate Minority Leader Chuck Schumer on Monday attended a vigil for victims of the Hannukah stabbing near New York.
Five people were stabbed and slashed in the Saturday attack, in Monsey, north of the city.
Grafton Thomas, 37, was held without bail after appearing in federal court in White Plains on five counts of obstructing the free exercise of religious beliefs by attempting to kill with a dangerous weapon.
Schumer said the attack was part of a rise in anti-Semitic hate crimes in New York and across the US.
New York State Attorney General Letitia James said authorities were worried about the possibility of copycat attacks and urged the community to be the "eyes" of law enforcement.
"We are also concerned, obviously, about individuals who might copy the crime of this individual, of the suspect. And I urge the entire community of New York State to be the eyes and to be the partners of law enforcement," she said.
"If you see anything it's important that you say something and that you reach out to law enforcement or the office of attorney general."