Much of the police activity has been focused on New York’s Central Park which seems to have formed part of the gunman’s escape route.

The lake was trawled for a second day on Sunday and a discarded backpack found nearby contained a jacket and some banknotes from the board game Monopoly but no gun, sources told CBS.

Police believe he entered the park on a bike moments after the shooting, then caught a taxi after leaving the park on the Upper West Side.

Images released over the weekend show the suspect masked in the back of the taxi heading uptown to Port Authority bus terminal near Washington Heights.

He has not been spotted on any cameras leaving the station so the presumption is that he made his escape by bus.

It is the same way he arrived in the city, 10 days before the shooting, on a Greyhound bus that originated in Atlanta.

He then checked into a hostel where he momentarily revealed his face to the receptionist, giving police their clearest image yet.