Louis Tomlinson's sister Félicité has died. As The Sun reports, the social media influencer collapsed in her London studio apartment on Wednesday (March 13). A friend promptly dialed 999 but paramedics were not able to revive her and pronounced her dead at the scene. Her cause of death has been identified as a heart attack. She was only 18 years old.

"Félicité was an absolutely adored young woman who was loved by Louis and her whole family. They are all totally devastated, as you can imagine," a source close to the Tomlinson family told the outlet. “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.”

Her last Instagram post came on Sunday (March 10). As soon as news of her passing broke, Félicité's 1.3 million followers flooded her comments with kind words.

The tragic news comes just a week after the former One Direction singer released a single called "Two of Us," which he wrote for his mother who died after a short battle with leukemia in 2016.

“I just feel like musically, I almost needed to get this song off my chest,” he said in a statement about the song. “People say writing is a part of therapy and in a way, I feel like I’d been avoiding writing this song because I knew I only had one chance to get it right. I don’t mean to be too soppy about it, but if 'Two of Us' can help just one other person who's going through the tough time that I went through, then that would make me really happy.”