Taylor Swift is "deeply saddened" by the sudden death of actress Hayden Panettiere, who passed away at 36. A source close to Swift told Page Six that the singer was "shocked" and "deeply saddened" by the news.

Swift and Panettiere shared a neighborly connection when both resided at The Adelicia apartment complex in Nashville. Panettiere lived there starting in 2012 while filming the ABC series "Nashville," and Swift purchased a penthouse in the building in 2009.

Their paths crossed occasionally, and Panettiere once recounted an instance where Swift came to her aid. During a 2012 appearance on "Jimmy Kimmel Live!," Panettiere explained that she needed a guitar for a songwriting session and had left hers in her trailer. After texting several people, Swift's security guards delivered a guitar to her.

"Taylor and Hayden were always friendly with each other and had a really nice rapport," a source told Page Six. "They lived in the same apartment complex in Nashville for a while and would cross paths from time to time."

In a 2012 interview, Swift referred to Panettiere as a friend and neighbor. She recalled an early meeting where Panettiere humorously stated, "I just need you to know, my character is not based on you."

"Hayden always spoke very highly of Taylor and was supportive of her, and there was always a mutual respect between them," the insider added. The two also saw each other at various events over the years and "always got along really well."

Panettiere died Sunday in Greenville, South Carolina, her family confirmed. Authorities responded to a residence after an "unresponsive" female was found in "cardiac arrest." Life-saving measures were administered but were unsuccessful.

A cause of death has not yet been officially determined, with toxicology results pending. Panettiere's father, Skip Panettiere, announced her death, describing her as "an incredible light and a force of nature." He requested privacy for the family as they process their loss. Panettiere is survived by her 11-year-old daughter, Kaya, and her parents.