Man arrested for alleged threats against NYC Jewish community

One of the men arrested in connection with an alleged threat to attack synagogues in New York City told police he operates a white supremacist Twitter group that he said "is really cool," according to a public criminal complaint Sunday following his arraignment.

Christopher Brown, 21, was arrested Saturday for allegedly making threats against the New York City Jewish community, authorities said.

The Suffolk County, New York, man made a series of increasingly concerning statements about attacking a synagogue in New York City, according to police sources.

Brown tweeted antisemitic threats under the username "VrilKhan" and told detectives, "I have a sick personality," the complaint said.

The threat, which was uncovered Friday by NYPD counterterrorism officers and FBI agents, did not involve a specific synagogue, police said.

An intelligence alert was issued that included a photo of the man, identified as Brown, stated the individual had allegedly "made recent threats to unknown Jewish Synagogues in the New York Area."

"Sharp-eyed" MTA police officers spotted the man entering Penn Station in Manhattan with another individual on Saturday, where he was found with a knife, according to NYPD Commissioner Keechant Sewell.

Police said Brown met another man, Matthew Mahrer, 22, at St. Patrick's Cathedral and had purchased a gun for $650 in Pennsylvania when he was arrested at Penn Station by two MTA police officers.

Brown was in possession of an 8-inch military-style knife with a 4-inch blade, a Swastika arm patch and a ski mask, according to law enforcement.

A subsequent search of an apartment where the suspect visited turned up an illegal Glock 17 firearm, sources said.

A 30-round magazine and several other items were seized in the search, police said.

"As a joint investigation now continues to establish a strong prosecution, Police Department commanders are strategically deploying assets at sensitive locations throughout New York City," Sewell said.

Brown, of Aquebogue, New York, has been charged with making a terroristic threat, aggravated harassment and criminal possession of a weapon, police said.

He pleaded not guilty at his arraignment and was ordered held without bail.

Mahrer, who hails from Manhattan, has also been charged with criminal possession of a weapon in connection with the incident, according to police.

Mahrer pleaded not guilty to weapons charges. Bail was set at $150,000.

Federal prosecutors are still considering additional charges, sources said.

It is unclear if the two men have an attorney who can speak on their behalf.

"A potential tragedy was averted when they were intercepted by police officers at Penn Station, given that online postings indicated an intent to use these weapons at a Manhattan synagogue," Manhattan District Attorney Alvin Bragg said. "Hateful antisemitic targeting of synagogues is deplorable."

The arrests come more than two weeks after the FBI announced the "broad threat" to New Jersey synagogues on Twitter and urged people to "stay alert" and "take all security precautions."

The FBI later said it identified the source of the threat made against an unspecified New Jersey-area synagogue. Once the young man was located, authorities realized there was no threat, sources said.

An 18-year-old man from Sayreville, New Jersey, was subsequently arrested and charged with one count of transmitting a threat in interstate and foreign commerce, the Justice Department said.

ABC News' Teddy Grant contributed to this report.