EXCLUSIVE DETAILS: Hayden Panettiere Was Involved in Tragic Love Triangle With Brian Hickerson's Brother Zach Dating Back SEVEN Years — as Cops Confirm Both Men Were at the Scene Where She Died

Hayden Panettiere was reportedly once involved in a tragic love triangle with her on-and-off boyfriend, Brian Hickerson, and his brother, Zach, RadarOnline.com can reveal.

The trio was reunited in a Greenville, South Carolina, apartment over the weekend, when the 36-year-old Heroes star suffered what has been called a fatal heart attack.

As Radar previously reported, Panettiere and Zach allegedly had a romantic relationship in 2019, as Brian was behind bars for attacking the actress. The two were spotted holding hands on the streets of New York, reportedly infatuated with each other.

"They were walking hand-in-hand, talking and laughing together," an eyewitness revealed at the time. "She was jumping up and down, making funny faces, and he was flexing his muscles and laughing. They looked happy together."

An insider told Radar at the time that Zach and Panettiere's relationship lasted at least two months.

"It’s a very strange set of circumstances," the insider said at the time, pointing out the romance came while Panettiere's relationship with Brian was "off again."

"I don't know if it's better than the alternative," said the concerned pal. "How strange it may be, the one positive thing about this is that Zach certainly does not have the violent temper that Brian has."

The pairing apparently didn't sit well with Panettiere's family either.

"Those close to Hayden are not going to pretend to understand it or condone it," the informant said. "But there’s nothing anyone can do.

"She has been reluctant to talk about it because she knows how people feel — it's definitely something she would not want to discuss. And she doesn’t want to share too much, especially because of what’s going on with Brian and his legal issues."

Panettiere and Brian began dating in 2018, but their relationship quickly became volatile, and he was arrested several times for domestic violence during their time together.

Despite the rumored side relationship fizzling out, Panettiere apparently remained close with both brothers, and the three were sharing a rented Airbnb in South Carolina when Zach reportedly found her unresponsive in an armchair on Sunday, August 16.

The brothers called 911 when Panettiere would not wake up, according to the police report, which noted both brothers were present when "EMS attempted to perform life-saving methods for an extended amount of time before they called a time of death" at 2:31 p.m. local time.

Zach reportedly referred to Panettiere as "his brother's girlfriend," and was described as being "very emotional" as paramedics were performing CPR on Panettiere.

The first responder also noted that Brian "did not become emotional until EMS declared her officially deceased."

Although the death was originally ruled a heart attack, a 911 dispatcher could be heard in the audio of the emergency call saying that Panettiere had suffered a "suspected overdose."

The Nashville star has a long history of drug abuse and addiction and had recently been reeling from a bad back.

According to the police report, Brian showed police a "bag of medication" that Panettiere had been taking at the time of her death, which she had kept inside the apartment complex.

A container of Narcan – a nasal medication used to treat an opioid overdose – was also found on a mattress at the property.