What was Hayden Panettiere's brother's cause of death? Inside the tragic story of her graffiti-artist younger sibling Jansen

Hayden Panettiere has opened up about her brother Jansen's February 2023 death at the age of 28 from an undiagnosed heart condition for the first time.

The actress and singer, 35, told People Wednesday, 'He was my only sibling, and it was my job to protect him. When I lost him, I felt like I lost half of my soul.'

At the time of Jansen's death, Panettiere's parents Lesley Vogul and Skip Panettiere said in a statement that his 'sudden passing was due to cardiomegaly (enlarged heart) coupled with aortic valve complications.'

The New York-born entertainer said that she dealt with agoraphobia in the wake of the high-profile family tragedy.

The Heroes actress said she put on weight - 'I just ballooned out,' she told the outlet - amid a spike in 'stress and cortisol' levels as she dealt with the tragic event.

'I didn't feel confident to put on clothes and get out of the house, but I also knew that I needed to get out and keep moving or I'd never stop looking and feeling this way,' Panettiere said. 

She added, 'It became a destructive hamster wheel of, do I feel good enough to go out?'

The Nashville star said she has gained a measure of wisdom in the wake of the tragic events.

'When something that massive has happened to you, you really learn to pick your fights and just not let the little things upset you,' Panettiere said. 'Because once something so horrific, so deep, so catastrophic happens in your life, there's not much that can really rock you.'

Jansen Panettiere, a graffiti artist, had been found dead at his Nyack, New York, apartment on February 19, 2023.

Jansen 'seemed to have sobered up' have a stint in drug rehab the previous year, sources told DailyMail.com last year, before he had relapsed into bad habits.

Neighbors indicated that Jansen used the narcotic Oxycodone and had been 'popping them like gumballs' in the years ahead of his premature passing. They said that a 'shabbily dressed' Jansen appeared 'wasted' when he would arrive at his home in the middle of the evening.

'He'd come out of a car at 4 a.m. wasted,' a neighbor said. 'He said he was just coming back from a shoot. He looked destroyed.'

The neighbor praised Jansen as 'very friendly and generous,' and a 'very nice guy,' adding 'he would always offer me help.'

The neighbor said that after Jansen 'disappeared' for a time before 'he left for a year' after 'his father came and got his stuff out and said, "I have to get him out of here."'

Said the neighbor: 'When he left he probably went into rehab ... when he came back he looked okay in the beginning. He looked like a different person. He came back straightened up. Then he went downhill from there.'

Panettiere told People that her brother's passing is something she 'will never be able to get over.'

She added, 'I will always be heartbroken about it. I will never be able to get over it. No matter how many years go by, I will never get over his loss.'

Panettiere appears in the upcoming movie Amber Alert, which is due in theaters September 27.