The new series, which stars Stephen Merchant and Sheridan Smith, tells the story of four men killed by Stephen Port and focuses on their families' fight to uncover the truth of what happened to them following a flawed police investigation.
Many watching the three-part series were shocked at the police's handling of the investigation, prompting viewers to take to Twitter. One person wrote: "#FourLives is already SO heartbreaking and I am already SO angry at the police treatment," while another added: "This is both chilling viewing and totally infuriating at the failings that led to more murders #FourLives."
Watch: Trailer for BBC drama 'Four Lives'
A third person commented: "I read last night about the true story. Then not long into it #FourLives, I’m already feeling the rage."
While fans of the show were shocked by the harrowing story, they praised the quality and importance of the new drama. One person tweeted: "Such great writing and a brilliant cast in #FourLives but a truly upsetting watch," while another added: "Four Lives is a hard watch, but a must-watch. This is heartbreaking."
Viewers were also quick to praise Stephen Merchant's "chilling" performance as Stephen Port, also known as the Grindr killer. One person took to Twitter, writing: "Merchant is suitably terrifying in this #FourLives," while another added: "Stephen Merchant is chilling in his role in #FourLives."
Sheridan Smith was praised for her performance as Sarah Sak
A third person agreed, tweeting: "@StephenMerchant is criminally underrated as a dramatic actor."
Many also applauded Sheridan Smith for her role as Sarah Sak, the mother of one of Stephen's victims, Anthony Walgate. One person tweeted: "Powerful performance from @Sheridansmith1," while another added: "#FourLives @Sheridansmith1 is so fabulous at portraying real women in extraordinary circumstances."
Four Lives will air on Tuesday 4 and Wednesday 5 of January at 9pm on BBC One.
Like this story? Sign up to our newsletter to get other stories like this delivered straight to your inbox.
Watch: Highlights from 2021