Protests in Hong Kong descended into violence on Tuesday as police shot a protester and fired tear gas as black-clad demonstrators threw gas bombs.

Hong Kong police shot a protester at close range, which left him bleeding from his shoulder, in a fearsome escalation of anti-government demonstrations that spread across the semi-autonomous Chinese territory.

Police published a video on Facebook confirming that an 18-year-old-man had been shot and was sent to the Prince Margaret Hospital in a conscious state.

"At around 4 p.m. on Tai Ho Road in Tsuen Wan, a large group of rioters were attacking police officers. Despite warnings from the police, the assailants still continued the violent attacks. The police officers' lives were under serious threat. To save his own life and his colleagues' lives, he fired a live shot at the assailant," the police official said in the video, according to a translation.

"The police do not wish to see anyone injured in the incident ... Here we must warn again all rioters must stop illegal acts."

While officers have previously fired warning shots in the air on multiple occasions during Hong Kong's monthslong anti-government protests, this is the first time a protester is known to have been shot. It came as thousands in mainland China celebrated the 70th anniversary of communist rule.

Hong Kong police fired water cannons to break up the increasingly chaotic crowds outside government buildings and across the city. Rail operator MTR also had to shut down all train services.

Chery tweet: Post rounds of tear gas in Admiralty, Hong Kong

Early Tuesday, local politicians gathered inside the Convention and Exhibition Centre in Wan Chai to observe the flag-raising ceremony. Outside, two helicopters were seen flying across the harbor, carrying the Chinese national flag and Hong Kong flag.

Oct. 1 marks the 70th anniversary of the People's Republic of China. While Beijing is expected to showcase its largest military parade yet, the special administrative region also has the day off as a national holiday.

The city's embattled leader Carrie Lam is in Beijing to celebrate the National Day. Hong Kong usually hosts celebratory events for the PRC's anniversary, but this year the fireworks and festivities were cancelled.