Hong Kong police fired tear gas and rubber bullets at pro-democracy protesters throwing petrol bombs in the Asian financial hub on Tuesday (October 1) as its Chinese rulers celebrated the 70th anniversary of the founding of the People’s Republic.

Now-viral video captured the moment when a police officer points a pistol at a black-clad 18-year-old protester at point blank range and fires a round, after which the young man falls to the floor.

Warning: Graphic video

The footage, filmed during a chaotic melee in the Tsuen Wan area of the city, is the first known instance of a protester being shot with live ammunition during weeks of clashes between police and pro-democracy campaigners. Police confirmed the incident in a statement, arguing the officer acted in self defense. “A police officer’s life was seriously endangered. In order to save his and other officers’ lives, they fired at the attacker.”

Cat-and-mouse clashes spread from the upmarket district of Causeway Bay to the Admiralty area of government offices on Hong Kong island, with many protesters arrested.

Violence also escalated across the harbour to Kowloon and beyond to the New Territories in the most widespread unrest in nearly four months.

At least 31 people were wounded across the territory, one critically, the Hospital Authority said without giving details. Indonesian journalist Veby Mega Indah was reportedly injured after being struck by a projectile fired by authorities towards protesters.

Police fired water cannon and volleys of tear gas to disperse protesters who were throwing Molotov cocktails outside central government offices in the Admiralty area, and ordered the evacuation of the Legislative Council building next door.

Police said “rioters” had used corrosive fluid in Tuen Mun in the west of the New Territories, “injuring multiple police officers and reporters.” No details were immediately available.

The territory has been tense for weeks, with protests often turning violent, as authorities tried to avoid activists spoiling Beijing’s birthday parade at a time when the central government is already grappling with a U.S.-China trade war and a slowing economy.

By the afternoon, police and protesters were involved in standoffs across Hong Kong, with the streets littered with tear gas canisters and other debris.

You can watch more of our recent coverage of the Hong Kong protests here.