Authorities say the suspect, wearing a scarf over his face and carrying a large knife, knocked on a rabbi's door in Monsey, N.Y., around 10 p.m. on Saturday, before entering and stabbing gatherers, including the rabbi's son.
Fifty to 60 people were inside the synagogue, which is connected to the home, at the time.
No one was reported killed after the Rockland County attack, but several were injured - including the rabbi's son - in what was the latest of almost a dozen incidents of violence against Jews in the area in recent weeks, including eight in Brooklyn and a deadly shooting in Jersey City.
Rockland has the largest Jewish population per capita of any U.S. county, with 31.4 percent, or 90,000 Jewish residents. Last month in Monsey, a man was stabbed while walking to a synagogue.
This time, a witness said the suspect said, "No one is going anywhere" before he launched the attack.
Victims were rushed to nearby hospitals, with no official details on their injuries.
The attack is just the latest in a series of anti-Semitic hate crimes to sew fear in the region. That's in addition to other hateful incidents targeting the black, Latino and LGBT communities, he said. He later held a news briefing on the attack, calling it evidence of a "cancer in the body politic" and saying it was fueled by intolerance. We must be extremely forceful in our denouncement of such hate or violence. "I don't think any of us want to live in a police state", Kennedy said.
Leaders around the state have expressed concern about anti-Semitism in the county, after an advertisement this August said County Legislator Aron Wieder - an Orthodox Jew - is "plotting a takeover" that threatens "our way of life".
Staten Island had several anti-semitic incidents earlier this year.
"I believe the situation has gotten so bad, frankly, that we need to increase our legal enforcement", Cuomo said Sunday during a televised press briefing.
As authorities began investigating the stabbings, officials shared messages of solidarity and resilience.
New York State Attorney General Leticia James said she was "deeply disturbed" by Saturday's incident. "So many Jewish families in our city have close ties to Monsey. We must confront this surge of antisemitic violence, prioritize the fight against bigotry, and bring people together - instead of dividing people up". "We'll use every tool we have to stop these attacks once and for all", he said. "We stand with all our communities facing hate". The rabbi led the service at the synagogue later, he said.
Trump's daughter and senior adviser Ivanka Trump, who is Jewish, commented earlier on the stabbing assault, tweeting, "The vicious attack of a rabbi in Monsey, NY last night was an act of pure evil".