The FBI released the name as Mukhammadzoir Kadirov of Uzbekistan, born November 5, 1984.
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The FBI tweeted that anyone with information about him should contact them at 1-800-CALL-FBI. On Wednesday, the Federal Bureau of Investigation released a poster saying it was looking for Kadirov, only to announce less than 90 minutes later that it had found him.
Earlier in the day, a USA government source told Reuters that Saipov had been in contact with another individual individual who is now under investigation by the FBI for suspected terrorism-related activities.
Prosecutors allege Saipov had been planning the attack for weeks and that he was inspired by the Islamic State terror group.
Saipov was charged Wednesday with terrorism crimes. The man, an Uzbek national, had not been named a suspect in the attack, but authorities said he may have information on Tuesday's attack.