Shoppers at Plaza Hollywood told RTHK on Friday that they were shocked on hearing of the brutal knife attack, which left two women dead.
Ashley, who lives in Diamond Hill, said she's worried about dining out at the mall.
"I feel very shocked when I saw the online video. I am worried about my safety. It is not common to see this kind of incident in shopping malls. I think it was very brutal," she said.
Another shopper, Patrick, also said he would be more careful when he's out and about.
"I just can't believe that something like this would happen in Hong Kong. I've never heard of anything like this for the past 15 years I lived here... I still think that Hong Kong is a safe place in general but there may be a little bit of concerns. So I'd be a bit more careful when I dine out," he said.
Meanwhile, the Social Welfare Department has advised people not to share the video of the attack, which has been circulating online.
It also urged those who experience emotional distress after watching the video to seek professional help.
The department said people can call its 24-hour hotline on 2343-2255 for immediate telephone counselling, support and referral services.
They may also call the hotline of the Hong Kong Red Cross on 5164-5040 for assistance.