MIDTOWN, Manhattan (WABC) -- A 21-year-old Aquebogue man was arrested at Penn Station after he made online threats to attack a New York City synagogue, threats that Mayor Eric Adams said were not idle.
Christopher Brown told investigators he has a "sick personality" and tweeted that he was going to ask a priest "if I should become a husband or shoot up a synagogue and die," according to the criminal complaint.
Police recovered a Glock semi-automatic firearm with an extended 30-round magazine and laser sight a large hunting knife, a black ski mask, and a Nazi armband, prosecutors said.
"This was not an idle threat," Adams said. "This was a real threat."
The NYPD, the New York State Police and the two main departments on Long Island have increased security at synagogues and other Jewish institutions as a result of the threats and Adams said the extra protection for the city's 1.6 million Jews would continue through Hanukah.
"We're always concerned about copycats," Adams said. "No one should ever feel threatened walking into their synagogue or place of worship."
Brown and another man, Matthew Mahrer, 22, were arrested Friday night after MTA police officers spotted them entering Penn Station following a notice from the Joint Terrorism Task Force.
"They had full descriptions from the other law enforcement," MTA chief Janno Lieber said.
It all started with Mitchell Silber's group, part of the United Jewish Appeal/Federation. Silber is a former NYPD intelligence official who now runs a private initiative to help protect those 2,000 Jewish institutions across the city.
On Friday morning, one of his intelligence analysts sat down at a computer programmed to scrub the internet for certain key words.
"There's a whole list of alerts that have come through overnight and our analysts start to go through them," Silber said.
One poster in particular stood out for the wording of his tweets.
"And they say ok this looks like something that's gonna be actionable," Silber said.
The NYPD and FBI subpoenaed Twitter for the user's IP address, and by the evening, they had submitted his picture to every cop in the city.
Since the recent takeover of Twitter by billionaire Elon Musk, Silber says computerized filters have seen hate-filled tweets increase fivefold in just a few weeks.
"The conversation just this afternoon was you know like from Jaws: I think we need a bigger boat. Should we be doing this 24/7? How do we cover the volume, the sheer volume," Silber said.
Brown was said to have posed a threat to an unidentified synagogue, according to the FBI. Mahrer was subsequently identified as an associate.
"We have no information there is any continued threat to the Jewish community in connection with this case," said the FBI's Michael Driscoll.
Brown and Mahrer have each pleaded not guilty to state charges. Federal prosecutors are still deciding whether additional charges are appropriate.
Brown told police he operates a white supremacist Twitter group that he said "is really cool," according to a criminal complaint made public Sunday following his arraignment.
A man who said he lived with Brown, his sister and his mother said that the suspect has schizophrenia. That man, Paul Higgins, said the suspect's mom and sister are not doing well.
Neighbors who knew Mahrer were tight-lipped Monday but said they were shocked because they say he is Jewish and his grandfather is a Holocaust survivor.
Police said Brown met Mahrer at St. Patrick's Cathedral and had purchased a gun for $650 in Pennsylvania.
"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," said Manhattan District Attorney Alvin Bragg. "Hateful anti-Semitic targeting of synagogues is deplorable."
In a tweet on Sunday, New York Gov. Kathy Hochul said she had directed State Police to ramp up support for communities that could be targets of hate crimes.
Many in the Jewish community are already on edge after a disturbing threat was made online two weeks ago by a New Jersey teen.
Submit a tip or story idea to Eyewitness News