Fourth-year electrical and electronic engineering student Lin Zhenxing was waiting for the lift with a friend, Mr Liu Yan, when they spotted Mr Widjaja - alleged to have stabbed his final-year project supervisor, Associate Professor Chan Kap Luk, during a meeting - sitting on the rooftop of a link bridge three floors below them.
Mr Lin whipped out his mobile phone to record Mr Widjaja through a glass window, for about eight seconds, before he called campus security using the phone.
Meanwhile, Mr Liu, a Chinese national, called the police.
While both men were making calls, Mr Widjaja allegedly pushed himself off the rooftop, falling four storeys to his death.
The phone's memory card, which contained the footage, was handed over to police at the scene.
It was screened in court yesterday at the fourth day of the coroner's inquiry into Mr Widjaja's death on March 2.
A total of 10 witnesses - including NTU staff and students, Mr Widjaja's online 'wife' and a forensic expert - took the stand.
It was also the first time Mr Widjaja's family, who had flown in from Indonesia, viewed the footage.
The footage was grainy and shaky and showed Mr Widjaja sitting by himself on the rooftop of the bridge, first looking down and then to his right - before the clip ended. His legs, shorts and T-shirt were seen to be covered with blood.
