Liam Payne’s erratic behavior escalated after girlfriend Kate Cassidy left vacation before his death

Liam Payne’s behavior began to spiral after his girlfriend, Kate Cassidy, left their vacation, a source close to Cassidy revealed to PEOPLE. The One Direction star, 31, died after falling from a third-floor balcony at the CasaSur Palermo Hotel in Buenos Aires on Oct. 16. “You could see from the Snapchat videos, he was a different person around her,” the insider shared, noting that Cassidy had been by Payne’s side throughout his recent legal troubles with ex-fiancée Maya Henry.

Cassidy, 25, stood by Payne amid his struggles, according to the source: “She had been super supportive of him through all the legal drama and very much stood by him.” Payne and Cassidy were first seen together in October 2022, keeping their relationship mostly private but occasionally sharing moments on social media.

Payne’s death occurred after hotel staff reported his erratic behavior, including “trashing” his room, to emergency services just minutes before he fell from the balcony. Police later found Payne’s room “in total disorder,” and a partial autopsy revealed multiple substances, including “pink cocaine,” in his system at the time of his death.

The Teardrops singer’s body will remain in Argentina until the autopsy is completed, officials told PEOPLE. A preliminary autopsy indicated Payne died from multiple injuries and hemorrhages, with coroners confirming his fatal head injuries were consistent with a fall from a height .