But the K-pop industry has had this exact same conversation before, when Sulli's fellow SM Entertainment colleague Jonghyun, of boy band SHINee, killed himself nearly two years ago.
Despite multiple suicide attempts and deaths, and lawsuits over malicious posts, the toxic online culture surrounding South Korean entertainment persists.
It is still thriving even as a nation grieves for Sulli. Her f(x) bandmate Victoria, who has yet to respond to the news on Weibo, has had her silence criticised as "heartless" by some netizens.
Sulli's former boyfriend, hip-hop artist Choiza, has seen his Instagram account flooded with comments blaming him for her death. They broke up in 2017.
Social media can be hateful and malicious, but the billion-dollar K-pop industry seems particularly primed for such toxicity to thrive.
For one thing, a lot of South Korean stars have public social media accounts, like Instagram, to promote their work and engage with fans. Many seemingly appear to manage these accounts on their own, posting videos of themselves before bed, for example.
That is partially why K-pop stars are globally famous - they create content frequently and are extremely accessible.
While accessibility brings them fans, it also makes them much more vulnerable to attacks like malicious comments or untrue rumours. For example, a fake nude photo of girl group AOA's Seolhyun circulated wildly on the Internet last year.
The vitriol K-pop stars are forced to reckon with is often exacerbated, given the notoriously competitive blocs of fans.
Everything in K-pop is a competition. YouTube views, award show wins, music show wins, Instagram followers, Twitter topics, unofficial polls on which idol has the most beautiful eyes - K-pop fans can and will vie over everything, in part because of how crowded the industry has become.
There are hundreds of active groups and because so many idols have embraced social media, it is easy for fans to leave hateful messages online for rival groups.
Even fans of the same group can start wars among themselves over resources, such as solo gigs, costumes, endorsement deals and drama projects, given to each idol.
The never-ending competition and comparison among fans and groups mean that idols live with negativity and intense pressure every day.
It takes a toll on idols' mental well-being, which comes on top of their gruelling schedules and the unrealistic expectations of fans for their idols to be faultless.
But it would be naive to assume that K-pop, a profit-driven industry, will become less competitive, or that the suicides of celebrities will shock people into behaving better.
Jonghyun died, but here we are again.
Perhaps the most practical thing to do moving forward is to ensure that K-idols receive professional counselling support. Ideally, they should feel comfortable speaking about mental health issues without the fear of stigma.
The tide is slowly changing in South Korea. Big Bang's leader G-Dragon, BTS rapper Suga, Super Junior's leader Lee Teuk, Twice's Mina and Momoland's Yeonwoo have all made public their battles with depression, anxiety and panic disorders. So did Sulli.
The next step is for management agencies and idols themselves to take charge of their mental health.
Adequate rest, regular check-ups with doctors and therapists, and swift action against death threats, false online rumours and pictures - this should be the norm and not the exception in K-pop.
Check out other Singapore celebrities who struggled and overcame mental illness:
This article was first published in The Straits Times.