A father involved in a custody battle threw his three-year-old son off the roof of a 52-storey New York building before jumping to his death.
Dmitriy Kanarikov, 35, was pronounced dead at the scene while his son Kirill, dressed in Christmas pyjamas, died moments later at a nearby hospital.
The tragedy came just three months after Ukranian-born Kanarikov vowed to be the 'best Dad and husband' during a post on Facebook.
Mr Kanarikov's estranged wife had custody of their son and and the father, who had visiting rights, was supposed to hand him over to her at a police station on Sunday afternoon.
A witness, who was at St Luke's Roosevelt Hospital when paramedics rushed the three-year-old there, said medical staff made desperate attempts to save his life.
Luis Ortiz said: "You could tell he was slipping away. They said the father was up there, but they didn't bring anyone else in. It was just heartbreaking. I have two kids of my own. They tried to do the best they could."
The New York Daily News reported that Mr Kanarikov died after plunging off New York's Lincoln Square tower with Kirill, who had been dressed in Christmas pyjamas.
Mr Kanarikov was declared dead at the scene, while his son died shortly after in hospital.
The Daily News told how the family's apparently happy life had fallen apart in recent months, with relations between the former couple becoming so difficult that they had to meet in a police precinct to drop off and pick up Kirill for visits.
Kanarikov is said to have collected his son at 10am on Sunday morning, and was supposed to take him back at 1pm.
It is thought Kanarikov recently argued with his estranged wife after one of them did not return their son at the right time following a visit.
Witnesses described watching the pair plunge from the 14th floor window after jumping.
Adam Gutierrez, who works in a nearby hospital, said: "I work in the hospital. I heard a boom!
"The sound, the way it sounded, they must've jumped from high up."
An investigation is taking place into the deaths.