Security camera footage showing the moment a university student fell to his death inside a Hong Kong car park as a protest took place nearby has been discovered by an inquest looking into last year’s incident.

The previously unseen footage, which was described on Friday by Coroner Ko Wai-hung as “very crucial”, was the first identified visual of the moment Alex Chow Tsz-lok fell from a multistorey car park in Sheung Tak Estate, in Tseung Kwan O, on the morning of November 4, 2019.

Its discovery could help the court assess the accuracy of previous testimony about the time and location of the incident, as well as influence forensic experts’ analyses in the evidence to follow.

The video clip, which was taken from a surveillance camera installed at Kwong Ming Court, a housing estate next to the car park, showed a black shadow descending from the building. But it was not clear enough to show the events preceding the fall.

“It appears that the black shadow in the footage is Tsz-lok,” Ko said.

Chow, 22, who studied at the Hong Kong University of Science and Technology, suffered extensive skull fractures, as well as bruises and swelling to his body after the fall. He died in hospital four days later.

Previous security footage at the car park last showed Chow walking towards the building’s third floor at 1:01.39am, when police officers were dispersing anti-government protesters at a nearby demonstration, but was unable to show the moment of the fall.

A police detective responsible for reviewing security footage earlier testified he found no useful materials from Kwong Ming Court.

But on Thursday, Ko revealed the discovery of the footage at the residential complex, which could largely shake up the course of the court inquiry.

The new footage gave the time of the fall as 12:51.37am, but Ko said that record was “obviously not the real time”, adding he had directed forensic experts to ascertain the precise time and landing point of the fall based on the footage.

Chow’s father, Chow Tak-ming, said outside court the new footage represented “one huge step towards the truth”.

He said he did not expect a breakthrough in the investigation from security footage initially discarded by police, but declined to comment on whether investigators had been negligent.

“Frankly speaking, at this moment, it does not matter who is right and who is wrong, and whether anybody has not done their job properly,” Chow said. “I am actually happy to learn about the coroner’s discovery, which may be one huge step towards the truth.”

He issued another public appeal, calling for residents at Kwong Ming Court who had knowledge about the fall to help the investigation.

Meanwhile, the coroner revealed that a separate security video, also discovered on Thursday, suggested government paramedics who previously testified had been wrong about the time they took Chow to hospital.

He stopped short of detailing what was in that footage, but said he had invited the director of fire services to hire legal representatives to attend the proceedings.

He adjourned the proceedings to next Tuesday to allow time for police to investigate further. He added that the inquest, originally slated for 25 days, might overrun in light of the latest developments.