For journalists covering conflicts, uneasy questions can arise: Is it possible to remain objective when witnessing injustice and brutality? When does it become too dangerous to continue working?

The film draws on the countless hours of footage that Lau shot as a freelance journalist, tracing the pro-democracy movement's yearlong arc from early optimism to the violent police crackdown and draconian legal overhaul that would ultimately silence the protests.

By the time the teargas smoke cleared, Hong Kong had changed irrevocably. And Lau, like most who participated in and covered the events, was also deeply transformed.

"I use my point of view as a journalist to talk about the whole movement," Lau told UPI in an interview in Busan. "What I felt and what I saw at that time is like a diary -- my psychological diary."

When he finally fled to Britain in 2021 amid sweeping arrests of journalists, activists and legislators, the 45-year-old said he was paralyzed with survivor's guilt and post-traumatic stress disorder.

"I spent almost two years avoiding the footage," Lau said. "It was so hard for me to return to the footage. Hong Kong is my hometown. I grew up there and I was forced to leave my home."

In one of the film's most horrifying sequences, police sweep through a subway car stopped in a station, spraying teargas and roughing up cowering protesters over several unbearable minutes. In another chilling scene, a young protester is shot in the chest by a live round and lays bleeding on the ground, ignored by the police as reporters and bystanders beg them to do something. (The 18-year-old survived.)

The line between observer and participant grows ever murkier as police begin targeting journalists, and Lau is standing nearby when an Indonesian reporter is blinded by a rubber bullet. He also second-guesses his decision not to warn a pair of fleeing protesters about approaching police, and then records them getting arrested.

"I was trying to keep objective but wondering if I should follow my heart," Lau said. "It was a struggle of conscience."

Ultimately, the filmmaker concluded that choosing to return day after day with his camera was the only answer he could live with.

"I decided to be involved," Lau said. "Being involved means that I record he truth, I record the police brutality. That is what I can do."

And while it is not as technically polished as some other productions, the film offers a unique and personal perspective as its through line. It also helps keep the story of the Hong Kong protesters, most of them achingly young, from blowing away like dust.

"I want the world to know what happened to Hong Kong and [to ask] what's next for Hong Kong," Lau said. "Being here at Busan is an opportunity to prove that the world has not forgotten Hong Kong."