A large crowd of demonstrators, including office workers in shirts and suits, gathered in a park and then marched through the city's commercial district in an unsanctioned rally on Wednesday, chanting anti-police and anti-government slogans.
Hundreds of people, wearing school uniform or black t-shirts, also staged a sit-in outside the school of the 18-year-old Tsang Chi-kin, who was shot in the chest as he and a group of masked protesters attacked officers with umbrellas and poles.
The international financial hub has been left reeling from the shooting, the first time a demonstrator has been struck with a live round in nearly four months of increasingly violent pro-democracy protests.
Tuesday witnessed the worst clashes of the summer, overshadowing China's military parade as the country celebrated 70 years of Communist Party rule.
Police defend shooting
The spiralling violence underscored seething public anger against Beijing's rule and shifted the spotlight from China's carefully choreographed birthday party.
Running battles raged for hours across multiple locations as protesters hurled rocks and petrol bombs. Police responded for the most part with tear gas, rubber bullets and water cannon.
As criticism rose, the police launched a spirited defence of their colleague who shot Tsang at a news conference on Wednesday, saying he feared for his life and the safety of his colleagues.
"He only had one option, that is to fire the gun to immediately resolve the danger," Deputy Commissioner Tang Ping-keung told reporters.
He said the use of force by the police on Tuesday was "undoubtedly lawful and reasonable".
But protest groups said the officer charged into the melee with his firearm drawn and failed to fire a warning shot as they condemned the increasing use of live rounds.
Video footage of the incident showed the officer firing directly at the protesters after a group attacked another officer in riot gear with rods at a demonstration in Kowloon. It is unclear whether the rods were made of plastic or metal.
Hospital authorities said the hospitalised teenager was in a stable condition.
More than 100 people were injured and 269 people were arrested during the unrest, police and hospital authorities said, as police fired tear gas and water cannon to try to disperse protesters.
Al Jazeera's Scott Heidler, reporting from outside the hospital where Tsang is receiving treatment, said the shooting could be a tipping point.
"Protesters have been on the streets for four months," he said. "This is a new territory we're in now."
Hong Kong's protests were ignited by a now-scrapped plan to allow extraditions to mainland China.
But they have snowballed into a wider movement calling for democratic freedoms and police accountability.
With Hong Kong leader Carrie Lam seemingly unwilling or unable to find a political solution, police have been left to deal with the increasingly angry protesters. Sentiment is hardening on all sides.
Some 96 people were brought to court on Wednesday morning to face charges of rioting in relation to protests held last month. They face up to 10 years in prison if found guilty.
The protest movement's main demands are an independent inquiry into police actions, an amnesty for those arrested and universal suffrage.
Beijing and Lam have said they are unwilling to meet those demands.