Speaking to reporters, Kelly said that information was gleaned from investigators' interviews of Dzhokhar Tsarnaev, 19, the younger of the suspects. His older brother, Tamerlan Tsarnaev, 26, was killed in a confrontation with police days after the Boston attack, after authorities said the pair fatally shot an MIT police officer and hijacked a car and its driver in the Boston area.
"The bit of information we had may have been words to the effect, 'coming to party in New York,' " Kelly said.
Dzhokhar Tsarnaev did come to New York City in November 2012 and may have visited once more after that, Kelly said. But he said that it was not yet known why the younger Tsarnaev, who remains in a Boston hospital, came to the city.
"The investigation is going forward," Kelly said. "Obviously we are counting on the Boston authorities to provide information in that regard, but we are doing our own investigation as well," he said.
A picture of Dzhokhar Tsarnaev in Times Square with four other people was posted on his Twitter account, Kelly said.