The Tsuen Kwai Tsing March was organised by a local preparation group, with Lam Kai-hong as applicant and Yu Ngai-ming as coordinator. After initial police objections to the gathering point, an agreement was reached on 24 August, and the march was approved — starting from Kwai Chung Sports Ground, proceeding along Kwai Fuk Road and Ma Tau Pa Road, and ending at Tsuen Wan Park. Thousands turned out despite steady rain, marching with umbrellas along sidewalks as agreed. Banners bearing the protest movement's call for "Five Demands, Not One Less" were visible along the route. Parents pushed strollers. At 4 pm, the organizers announced that participants could circulate freely through the rally area, noting that the tail of the march was still waiting to depart from the starting point.

Around 4 pm, some protesters began dismantling roadside railings near Texaco Road to set up roadblocks. At 4:40 pm, police announced that the Tsuen Wan Police Station report room was temporarily closed. Riot police arrived near Nina Tower on Yeung Uk Road at 4:48 pm. By 5:40 pm, officers raised an orange flag — warning of live ammunition — and fired multiple rounds of tear gas outside Yeung Uk Road Complex. Protesters responded with petrol bombs and laser pointers before withdrawing into the Tsuen Wan Plaza shopping centre, where they used fire hoses to wet the floors and block the entrances. Clashes moved between several neighbourhoods, with further confrontations in Sham Shui Po and Tsim Sha Tsui through the late evening. At the Cross-Harbour Tunnel toll plaza, protesters briefly blockaded the booths, allowing vehicles through without payment.

The day marked two firsts. The Specialised Crowd Management Vehicle — a water cannon — was deployed for the first time in the crackdown on the Anti-Extradition Law Amendment Bill movement, spraying twice within an hour. And in an alley near Sha Tsui Road and Chung On Street, as demonstrators confronted a group of about six police officers, a shot was fired into the air as a warning — the first use of live ammunition in the protest movement. Officers raised their firearms toward demonstrators and press. A middle-aged bystander spread his arms between the officers and the crowd, then knelt down pleading, "Don't shoot." An officer kicked him aside. He stood back up. Police later defended the kick as a "natural reaction" by an officer who believed his life was under threat. The three officers who had drawn weapons were quickly surrounded by journalists.

During police clearing operations around 7 pm, riot police surrounded and detained a 12-year-old boy near Yeung Uk Road, binding his hands with zip ties and ordering him to squat. His elbows were scraped and bleeding. A social worker on the scene shouted that the boy was under 16 and attempted to assist him. Officers told her this might constitute obstruction of justice. When reporters approached, they were threatened with batons and told to inquire with the public relations department. The boy was taken away in a private car. He was later confirmed to be a newly enrolled Form 1 student at Lingnan Hang Yee Memorial Secondary School. The school contacted his parents and arranged for social worker support. He became, at that moment, the youngest person arrested in the movement. Thirty-six people were arrested that day in total, ranging in age from 12 to 48.

The legal proceedings that followed the 25 August events stretched over years. A 25-year-old teacher who pleaded guilty to illegal assembly and assaulting a police officer was sentenced to ten months in prison, with the judge noting that a conviction would likely cost him his teaching post but declining to treat that as sufficient mitigation. A 21-year-old student who pleaded guilty to illegal assembly was sentenced to eight months. Among the seven defendants in the Yeung Uk Road illegal assembly case who went to trial, those convicted received sentences of around eleven months. The cases moved through Hong Kong's courts in the years that followed, each verdict accumulating into the broader record of what had happened that rainy Sunday afternoon in Tsuen Wan.