Mayor Bill de Blasio has been briefed on the incident, and divers with both the NYPD and FDNY are already searching the water, the mayor's spokesperson said.
"The helicopter reportedly is inverted in the water".
New York City Police Commissioner James O'Neill said the aircraft was registered to Liberty Helicopters, a sightseeing and charter service in New York, and was on a private charter "photo shoot".
The crash happened near the mayoral residence. The helicopter can be seen landing hard and tipping over.
The Eurocopter AS350 went down in the waters between the boroughs of Manhattan and Queens just after 7 p.m. ET, according to a Federal Aviation Administration spokeswoman. Helicopters fly people around the city for business, traffic reports, medical reasons and tourism.
Twitter footage captured the moment a helicopter crashed into the East River..
The other three were taken to hospital in critical condition.
Nigro and Police Commissioner James O'Neill said the rescue operation Sunday took place in a 4 miles per hour current in water about 50 feet (15 meters) deep, under challenging conditions. In June 2005, two helicopters crashed into the East River in the same week.
The National Transportation Safety Board are investigating the cause of the crash.