Law enforcement officials are seeking the public's assistance with information about Kadirov in relation to the deadly attack along West Street.
In that attack, Uzbek native and USA permanent resident Sayfullo Saipov, 29, drove a truck through cyclists and pedestrians, killing eight and injuring 12.
"We have found him and we will leave it at that", Federal Bureau of Investigation assistant director Bill Sweeney told reporters.
The person in touch with Kadirov's family says the two men knew each other only from their days as fellow drivers for the ride-sharing app Uber and were not close friends.
Jared Kushner hands over documents to Robert Mueller
The documents Kushner handed over were similar to those that he gave to congressional investigators earlier this year . Mueller is interested in possible obstruction of justice issues regarding the Comey's firing.
He was slated to be arraigned on terrorism charges Wednesday night.
Named as Sayfullo Saipov, the suspect drove a rented truck through a bike path, striking pedestrians and bicyclists, until he crashed into a school bus.
Saipov was shot in the stomach by a police officer and is being held in a Manhattan hospital.
It was the bloodiest single attack on New Yorkers since the September 11, 2001, suicide hijackings of jetliners steered into the World Trade Center.
Anyone with information about Saipov or this case can contact the FBI's toll-free tip line at 800-CALL-FBI (1-800-225-5324), the local FBI office, or the nearest U.S. Embassy or U.S. Consulate.