"I have spent days hoping that it was a mistake and somebody has got it wrong," Nicola Payne writes of her late brother

Liam Payne's sister shared a glimpse into the way the One Direction singer's family is handling their grief less than a week after his tragic death in Argentina.

Nicola Payne, one of Liam's elder sisters, wrote a public letter to her late brother on Monday, five days after the "Teardrops" musician fell to his death from a hotel balcony in Buenos Aires on Oct. 16. It turns out, she learned about Liam's death at age 31 from a news notification.

"I have posted about Liam and his achievements over the years with a proud sister alert and that has stood then, now and always," she wrote on Instagram. "When I saw the news pop up on my phone that you had left us I went cold, I wanted so much for this to be untrue. I have spent days hoping that it was a mistake and somebody has got it wrong. You were truly too good for this earth, you are an angel who just lived for making people smile and happy. You have always shown kindness to everyone you met and it shows with just how many people have confirmed what we always knew!"

"We don't have many pictures together as we never really did that as a family, we never wanted you to feel like you were in a room of fans, but we were your biggest fans always and forever. Your talent alone puts you miles ahead, but also you being you," Nicola continued. "I have been looking back at the messages from the night I had Ffion, how excited you were to meet her, the jokes we all shared and the laughter that you knew we all needed."

"You led your life with a motto of why bother doing something unless you are brilliant at it, and Liam you were certainly brilliant at everything you did! Unfortunately this cruel world is always too quick to judge someone from a few 5-second clips, they then think it entitles them to be able to speak like they know you. We knew you and we loved you," she concluded. "I hope you have finally found peace up there and that you'll continue to look after us all as you have done in life. We will make sure Bear knows about his daddy and how much you loved him, we promise this. See you soon Liam."

Nicola's family update comes the same day that ABC News reported that Liam's autopsy showed "pink cocaine" in his system, citing local sources. As TheWrap previously reported, his preliminary autopsy indicated his cause of death was "internal and external hemorrhage" from "multiple traumas."

Liam was found dead when emergency services were called to the CasaSur Palermo hotel last Wednesday. His death was classified as suspicious, "Although everything suggests that the musician was alone when the fall occurred and was going through some kind of outbreak due to substance abuse," according to a Thursday statement from the 14th National Criminal and Correctional Prosecutor's Office in Argentina.

The former 1D singer is survived by 7-year-old son Bear, whom he shared with Girls Aloud member and "X Factor" judge Cheryl Cole. Liam is also survived by his parents Geoff and Karen Payne, as well as sisters Ruth and Nicola.