Videos show the two women walking at the mall before the assailant stabs one of them with a 15cm (6-inch) knife in the back multiple times. The other woman pushes the man away and drags her companion a short distance before he catches up and continues to attack the first victim.

The assailant then punches the second woman, proceeding to once again stab the first multiple times.

Nobody comes to help for the duration of the attack as the second woman tries to intervene again and again, kicking him at one point.

The man leaves the first woman lying on the floor and chases after the second, whom he stabs and slashes.

Officers arrived at the scene within four minutes after receiving multiple reports from members of the public, police later on Friday said.

Another viral clip shows officers with shields and pepper spray approaching the assailant and ordering him to drop the knife. They rush him together, dragging him to the floor and handcuffing him.

Police said the two women were friends aged 22 and 26 and had been taken unconscious to United Christian Hospital, where they succumbed to their injuries at 6.06pm and 6.47pm, respectively.

According to the force, the suspect was a jobless man with a history of mental illness, who regularly required check-ups with a doctor.

According to police figures, crime in Hong Kong is at its lowest level since the city’s return to Chinese sovereignty in 1997. The data showed 8,830 of the 70,048 cases reported in 2022 were violent ones, a 7.9 per cent drop from the year before.

Statistics from the previous 10 years also indicated a steady decline in the number of woundings and serious assaults, dropping from 6,818 in 2012 to 3,614 last year.

However, the city in recent months has witnessed several violent incidents.

A 54-year-old woman in May was killed after being attacked with an electric saw and a knife near her home in Yuen Long. Police said she had suffered “multiple cut wounds to the neck and wrists and multiple stab wounds to the abdomen and chest”.

A source had said police were looking for Lau Hung-lee’s stepson, aged in his 40s, who had fled the city, over the killing on Kam Pok Road.

In April, eight people were arrested in connection with the murder of a 70-year-old man during a knife attack in Yuen Long the month before.

In a separate incident, three suspected triad members were detained for their alleged involvement in a daylight knife attack on a 34-year-old man in Sheung Shui.

Police had said they believed the attack was triggered by a dispute over money from illegal businesses involving hundreds of thousands of Hong Kong dollars.

Eileen Chung Lai-yee, a senior superintendent, said a preliminary investigation found there was “no concrete evidence” to suggest the two women had been linked to the assailant.

“The relationship between the victims and the suspect, as well as his motivation, will be the focus of our investigation,” Chung said on Friday evening.

Detectives from the Kowloon East regional crime unit are handling the case, which has been classified as murder.

Chief Executive John Lee Ka-chiu offered his condolences to the victims’ families on Saturday and stressed the attack was an individual case. He also vowed authorities would uphold law and order.

“I am saddened by the murder … Police have arrested the suspect and will spare no efforts in investigating the case,” he said.

Lee also urged the public not to share footage of the incident, as people could feel disturbed by the clips, instead encouraging everyone to show “more love and care” to their friends and family during the difficult time.

“Those who feel emotionally disturbed should seek professional help,” he added.

Steve Vickers, CEO of risk mitigation and consulting company Steve Vickers Associates, said anyone in the immediate vicinity of a violent attack should stay away from the assailant.

“At close range, a knife is just as dangerous as a pistol. Get out of the way, run,” he said.

“Make a loud noise to attract assistance and, as soon as possible, call the police or local security guards with precise information as to the incident and exact description of the culprit.”

Poon Wai-kwong, a nurse and disaster life support expert, advised bystanders to consider their own safety first before attempting to help any victims.

“Safety always comes first. You need to ensure your own safety before conducting any rescue,” he said.

Keeping oneself safe was the first priority, followed by making sure the surroundings were secure, and then caring for victims, Poon explained.

When tending to victims, he advised people: “If you see acute bleeding, you should apply pressure on the wound, using things such as gloves and plastic bags.

“These precautions can prevent major blood loss, which may lead to shock and then death. Then you should wait for the first responders to arrive and send the victims to hospitals.”

If a victim’s heartbeat had stopped, Poon recommended bystanders perform cardiopulmonary resuscitation (CPR).

Discussing a possible response to Friday’s incident, he said: “CPR is a must and should be done, as the women likely had no pulses and had suffered [cardiac] arrests.”

The disaster life support expert said CPR could help victims to pump blood after their hearts had stopped.

Meanwhile, Hong Kong Red Cross advised the public to prevent causing themselves any emotional distress by refraining from repeatedly watching video clips of the stabbings on television and social media.

“Both adults and children experiencing apparent emotional distress can seek professional help,” it added.

The NGO also said it was working with the operator of Plaza Hollywood to assist business owners and local residents, promising to provide psychological support to those in need.

Anyone seeking psychological support can call Red Cross at 5164 5040, as well as the Social Welfare Department’s hotline at 2343 2255 and the Hospital Authority’s 24-hour mental health service at 2466 7350.

Consultancy firm CEO Vickers said that although Hong Kong had seen some high-profile violent crimes in recent years, it was “perhaps the safest city in Asia from a public safety and crime perspective”.

“In reality, the very low level of murders is a credit to the city, our society and police force,” said Vickers, who worked for the city’s police force for 18 years before the handover.

“Frantic and ill-considered social media reporting and poor quality reporting has resulted in some overegged and hysterical headlines.

“Over the years, various murder incidents have received such treatment – everything from Hello Kitty to the Jars murders.”

The former police officer said the spotlight should instead be put on mental illness, especially after “pressure-cooker living conditions” amid the Covid-19 pandemic.

“In my experience, incidents often happen during hot weather or where individuals need medical treatment or have come off their medication,” he said.

Lawmaker Bill Tang Ka-piu, who sits on the Legislative Council’s security panel, described the case as “extremely shocking”, saying it was hard to imagine such an incident could happen in Hong Kong.

Warning the attack would make residents feel less safe, the legislator said revealing the findings of police’s investigation as soon as possible was the only way to ease public concerns.

Lawmaker and former security minister Lai Tung-kwok also expressed shock that the stabbings could occur in broad daylight.

Lai voiced his confidence in police and said he believed safety fears among residents would subside if authorities cracked the case in short order.

Additional reporting by Cannix Yau