Authorities believe he is the man who donned a gas mask, set off a smoke bomb and then fired 33 shots on a Manhattan-bound N train, wounding 10 people and leaving nearly two dozen others hurt in the ensuing chaos.
Investigators were examining social media videos in which the 62-year-old decried the United States as a racist place awash in violence and sometimes railed against Mayor Eric Adams.
"This nation was born in violence, it's kept alive by violence or the threat thereof and it's going to die a violent death," he said in one video. "There's nothing going to stop that."
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NYPD Commissioner Keechant Sewell called the posts "concerning," and officials tightened security for Adams, who was already isolating following a positive COVID-19 test Sunday.
James was taken into custody Wednesday after being spotted by bystanders wandering around the East Village.
The shooter fled in the chaos Tuesday, leaving behind the gun, extended magazines, a hatchet, detonated and undetonated smoke grenades, a black garbage can, a rolling cart, gasoline and the key to a U-Haul van.
That key led investigators to James, who has addresses in Philadelphia and Wisconsin, NYPD Chief of Detectives James Essig said. The van was later found, unoccupied, near a station where investigators determined the gunman had entered the subway system.
The ATF determined that James bought the gun used in the subway shooting in a pawn shop in Columbus, Ohio, in 2011.
Investigators believe James drove up from Philadelphia on Monday and have reviewed surveillance video showing a man matching his physical description coming out of the van early Tuesday morning, the official said. Other video shows James entering a subway station in Brooklyn with a large bag, the official said.
After the shooting, Essig said James boarded an R train that pulled into the station and went one stop before exiting at the 25th Street station. After that, James was seen again at a Park Slope subway stop just under an hour later before fading from view.
The gun and the purchase of a gas mask on eBay are among the pieces of evidence that elevated James from person of interest to suspect, sources told ABC News.
Investigators also grew more comfortable calling James a suspect after they re-interviewed witnesses who initially gave a height description of the gunman that did not match James' 6-foot-2 frame.
Authorities have at least one of James' credit cards and are able to track his purchase history.
Phantom Fireworks confirmed in a statement that James purchased products in Wisconsin believed to have been left behind in the 36 Street subway station.
At this early stage of the investigation, authorities have discovered no meaningful felony arrests in James' critical history, only a number of misdemeanor charges.
However, rambling, profanity-filled YouTube videos apparently posted by James, who is Black, are replete with violent language and bigoted comments, some against other Black people.
In one video, posted a day before the attack, he criticizes crime against Black people and says drastic action is needed.
"You got kids going in here now taking machine guns and mowing down innocent people," James says. "It's not going to get better until we make it better," he said, adding that he thought things would only change if certain people were "stomped, kicked and tortured" out of their "comfort zone."
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Several videos mention New York City's subways.
A February 20 video says the mayor and Governor Kathy Hochul's plan to address homelessness and safety in the subway system "is doomed for failure" and refers to himself as a "victim" of the city's mental health programs. A January 25 video criticizes Adams' plan to end gun violence.
(The Associated Press contributed to this report)
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