One Direction singer Louis Tomlinson's teenage sister, Félicité, died after suffering a heart attack, TMZ confirmed. The 18-year-old was at her studio apartment in London when she died.

According to TMZ, Félicité collapsed from a heart attack, and someone in the apartment called for an ambulance. Paramedics arrived at the scene and tried to revive her, but she was later pronounced dead at the scene. An official statement on the cause of death was yet to be revealed.

“Félicité was an absolutely adored young woman who was loved by Louis and her whole family,” a source told the Sun. “They are all totally devastated, as you can imagine,” the insider added. “She had so many friends and was such a positive happy person. It’s a massive loss to the world. She was a loveable, caring, bright, passionate, popular and beautiful young lady.”

TMZ reported, citing sources close to the family, that the teenager had absolutely no warning signs of an illness and they knew of no prior history of heart trouble. She did, however, suffer from sciatica — a type of pain that radiates along the path of the sciatic nerve, which branches from the lower back through hips and buttocks and down each leg.

Félicité, who was an aspiring fashion designer, was also a social media influencer – known as Fizzy – with over 1 million followers, TMZ reported. She was also reportedly planning to publish a book of her own poetry.

Back in January, Félicité posted on social media saying she stopped drinking and stopped smoking cigarettes.

Félicité was one of the seven siblings, with Louis being the oldest. The other siblings are Lottie, twins Daisy and Phoebe, and twins Ernest and Doris.

The One Direction singer is yet to publicly address his sister's death. The latest tragedy comes two years after the 27-year-old lost his mother to cancer in December 2016 when she was only 43. He recently released a song called "Two of Us," about him and his mom.

Louis Tomlinson
Louis Tomlinson performs on stage during Key 103 Live held at the Manchester Arena in Manchester, England, on Nov. 9, 2017. Getty Images/Anthony Devlin