In a tense stand-off Friday night, an officer fired a live round into the air in Yau Ma Tei, a police source confirmed.

He said a group of detectives were surrounded by protesters at the junction of Hamilton Street and Nathan Road and one officer fired a warning shot. He said nobody was injured.

This came after a day of grieving that rocked the city.

University president Wei Shyy announced Chow’s death at a graduation ceremony in the morning. Many in the crowd broke down in tears. The university announced classes would be suspended to mourn his death and Shyy later issued a public statement demanding a “thorough and independent investigation”.

Many Hongkongers took to the streets to mark Chow’s passing. Candlelight vigils were held in at least nine districts on Friday night. In response to media inquiries, the government expressed “great sorrow and regret” over the student’s death and promised that police would carry out “a comprehensive investigation” into the incident that took place early on Monday.

Secretary for Education Kevin Yeung Yun-hung offered his “deepest condolences” to Chow’s family.

But his death also triggered a radical reaction from some.

Although the exact circumstances of how Chow sustained a severe head injury after falling from a ledge of a car park in Tseung Kwan O remained unclear, dozens of masked protesters vented their anger on the university authorities and businesses with mainland China connections.

Within hours after the news was announced, the protesters went on a rampage on campus, vandalising Shyy’s residence and trashing at least three cafeterias, a Starbucks outlet and a Bank of China branch. Some chanted slogans demanding Shyy condemn police violence, which they blamed for Chow’s death.

Most mourners were peaceful. Some students and graduates brought white flowers to HKUST to commemorate Chow.

A fourth-year student at the university who was Chow’s primary school classmate said he was heartbroken.

He remembered Chow as a hardworking person full of positive energy.

“I could not have imagined something like this would happen to one of my classmates,” he said.

He also demanded the university president condemn police violence.

Shyy in the evening sent an email to all students and staff of the university, pledging that he would take up the matter with police.

“We saw the footage of ambulances being blocked by police cars and the paramedics walking to the scene, causing a delay of 20 minutes in the rescue operation of our student,” Shyy wrote.

“We demand clarifications from all parties – especially from police, regarding the cause of the delay in those most critical moments that might have saved a young life. We will be outraged if there is no acceptable explanation offered to us.”

Many also accused police of firing tear gas into the car park during a dispersal operation on Sunday night which lasted into the early hours of Monday, during which time the incident happened.

The clash was sparked by a group of people trying to disrupt a police officer’s wedding being held in a Tseung Kwan O hotel.

Chow reportedly fell from the third floor of a car park near the area of confrontation to the second floor, sustaining severe injuries to his head. It was unclear whether he was part of the group, why he was at the car park and what exactly caused him to fall.

Friday night, someone claiming to be Chow’s friend sent a WhatsApp record to local media outlet Initium, showing that Chow was last seen active at 1am.

He also sent a photo to a friend at 12.46am, which was taken from the second floor of the building, showing riot police in action on Tong Chung Street.

No sign of tear gas could be seen in the photo and it was unclear when it was taken or by whom.

Chow had been in a coma after the fall. He was sent to Queen Elizabeth Hospital in the early hours of Monday. Two operations were carried out to stop the swelling in his head but failed to improve his condition.

A spokesman for the hospital said on Friday it had referred Chow’s case to the Coroner’s Court for an inquiry.

Police denied that any officer had entered the car park between the time when Chow got into the building and when he was found.

“Clips showed that [between 12.26am and 12.49am when he was in the car park], Chow was alone and wandering at normal speed. He did use a mobile phone but did not have physical contact with anyone,” Kowloon East Superintendent Wu Ka-yan said.

He urged the public to wait for the Coroner’s Court report and said police would pass on their investigation findings to the coroner.

Chow was the first fatality from injuries sustained during a police operation in the city’s five-month social unrest, triggered initially by the now-withdrawn extradition bill that would have allowed criminal suspects to be transferred to mainland China for trial.

His death could become a new lightning rod, with some protesters and student representatives calling for a general strike and class boycott next week.

Confederation of Trade Unions (CTU) chairwoman Carol Ng Man-yee confirmed she had heard discussions about a strike next week but said no serious planning was done at this stage.

Thousands of protesters held candlelit vigils on Friday night in at least nine areas – Sha Tin, Kwun Tong, Tuen Mun, Central, Yuen Long, Mong Kok, Tsim Sha Tsui, Causeway Bay and Tseung Kwan O – with tear gas fired in Tsuen Wan and Sai Wan Ho.

Many also laid flowers at the car park where the tragedy took place and left messages written on stickers to express their grief.

“Rest in peace, classmate Chow,” one read. “You are a true son of Hong Kong,” another read.

The crowds refused to disperse well into the night, engaging in a stand-off with police.

In Mong Kok, some protesters occupied Nathan Road and set up roadblocks to disrupt traffic. Police used a robot to detonate a suspected explosive device after at least three blasts in the area amid a stand-off between protesters and officers.

Roadblocks were also set up in Sha Tin, Yuen Long and Causeway Bay.

In Tuen Mun, police unfurled banners warning protesters to disperse or face action. A footbridge at a Light Rail station was set on fire by some protesters.

By 11.26pm, 11 MTR stations including Sha Tin and Mong Kok had closed and all Light Rail services and the Disneyland Resort Line were suspended.

The MTR Corporation said a petrol bomb was thrown in Tsuen Wan station.

Protesters also vandalised the logo on Mong Kok MTR station, a phone booth in the district, facilities in other train stations, as well as shops such as Best Mart 360 and Maxim’s Cakes in Tsuen Wan.

An electricity box on Tong Ming Street in Tseung Kwan O was on fire, with explosive sounds heard at the road junction in the area.

This set an ominous tone for the weekend, when large protests are expected.

Meanwhile, at least seven pan-democrat legislators – Eddie Chu Hoi-dick, Lam Cheuk-ting, Raymond Chan Chi-chuen, Leung Yiu-chung, Kwok Ka-ki, Gary Fan Kwok-wai and Au Nok-hin – were arrested, or notified that they would be arrested, by police on Friday night on suspicion of interfering with other lawmakers attending a Legislative Council meeting on May 11.

On that day, pro-establishment lawmaker Abraham Razack was planning to chair a bills committee meeting on the now-withdrawn extradition bill when he was stopped by pan-democrats who said that he had not been duly elected, and that his meeting would have no legal effect.

Legco’s secretariat appointed Razack as chairman after pan-democrats used delaying tactics to stop the committee from electing a chair in a bid to slow work on the controversial legislation.

Additional reporting by Zoe Low, Victor Ting, Cannix Yau, Kathleen Magramo, Kanis Leung, Albert Han and Tony Cheung