NEW YORK — A Pakistan-born US citizen accused of driving a bomb-laden vehicle into Times Square and parking it on a street lined with restaurants and Broadway theaters was to appear in court Tuesday to face charges that he tried to set off a massive fireball, federal authorities said.Faisal Shahzad was on board a Dubai-bound flight at John F. Kennedy International Airport when FBI agents and New York Police Department detectives took him into custody late Monday, law enforcement officials said. One official said he claimed to have acted alone.Shahzad, 30, is a naturalized US citizen and had recently returned from a five-month trip to Pakistan, where he had a wife, according to law enforcement officials who spoke to The Associated Press on condition of anonymity because of the sensitivity of the investigation into the failed car bombing.Shahzad became a naturalized US citizen last year shortly before traveling to Pakistan, a federal law enforcement official said, speaking on condition of anonymity amid the ongoing investigation. Shahzad, was not known to the US intelligence community before the Times Square incident, the source said.US authorities "will not rest until we have brought everyone responsible to justice," Attorney Eric Holder said early Tuesday, suggesting additional suspects are being sought.Investigators hadn't established an immediate connection to the Pakistani Taliban — which had claimed responsibility for the botched bombing in three videos — or any foreign terrorist groups, a law enforcement official told The Associated Press on Tuesday."He's claimed to have acted alone, but these are things that have to be investigated," the official said. According to Police, the SUV bomb could have produced "a significant fireball" and sprayed shrapnel with enough force to kill pedestrians and knock out windows.A vendor alerted a police officer to the parked SUV, which was smoking. Times Square, clogged with tourists on a warm evening, was shut down for 10 hours. A bomb squad dismantled the explosive device, and no one was hurt.But Holder cautioned that Americans should remain vigilant. "It's clear," he said, "that the intent behind this terrorist act was to kill Americans."