Heartbreaking pictures show a family of five, including three children, killed on a tour helicopter that crashed into New York City's Hudson River. The photos show the family posing on the helipad just moments before the deadly crash.

Agustín Escobar, his wife Merce Camprubi Montal and their three children, aged four, five and 11, were killed in the crash, along with the 36-year-old pilot. Escobar was the CEO of Rail Infrastructure at Siemens Mobility and the former president of the technology company's Spanish branch. The crash took place around 3.15pm local time on Thursday, with witnesses saying they saw the helicopter “split in half” before it crashed into the water in a “sonic boom”.

Law enforcement sources told the New York Post that the family of five arrived in NYC from Barcelona earlier on Thursday.

It has also emerged that the helicopter pilot warned he needed to refuel just before the tragedy, which killed all six on board. The helicopter flew for approximately 16 minutes before going down.

The aircraft was operated by New York Helicopter, a local tour company. According to FlightRadar24 data, the chopper appeared to be an N216MH - a Bell 206L-4.

Witnesses said they saw the chopper "split in half" before it went down, and one reported the aircraft making what sounded like a "sonic boom."

Investigators say it is too early to say what caused the crash.

Dramatic video showed the helicopter sinking into the water as emergency crews rushed to the scene.