Story highlights Exclusive: Uncle says Pistorius's grief over killing of Reeva Steenkamp 'unthinkable'

Pistorius has grown a beard and is surrounded by photos of Steenkamp

CNN's Robyn Curnow first reporter to speak to 'Blade Runner' at uncle's Pretoria home

Pistorius charged with murdering Steenkamp on February 14; has court hearing Tuesday

Oscar Pistorius is a heartbroken man who has to live with the fact that he killed the love of his life, his uncle has told CNN in an exclusive interview.

For the past three months, the double amputee sprinter has been living at his Uncle Arnold's house in Pretoria. He has grown a beard because he doesn't want to be recognized, and has surrounded himself with photos of Reeva Steenkamp, his uncle says.

Pistorius is charged with murdering the 29-year-old model and law school graduate early on February 14, and faces a court hearing next Tuesday.

Arnold Pistorius described the runner's grief as "unthinkable" and says his heart bleeds for his nephew. "He's got photos in his room, photos all over the place. He's housebound, you know. He doesn't go out in public places.

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"What can you say if the person you love the most dies, and you were the instrument? How would you feel? It's unthinkable."

Pistorius says Steenkamp's death was an accident and that he mistook her for a burglar. The state says it was murder. A trial date has not been set.

The sprinter's agent has also spoken for the first time about the 4 a.m. call he received telling him there had been a shooting at the track star's home.

"It was the estate where Oscar (was) staying at, the estate manager's daughter phoned me from Oscar's phone. So I picked up the phone and saw it was Oscar's number and thought it was him phoning me. And just had this voice of a girl frantically on the other side shouting, 'Please, you have to rush over here, you have to come to Oscar's house,'" Peet van Zyl told CNN in an exclusive interview.

"I initially thought it was Oscar that has been shot. She said, 'No, no, no, no. Reeva's been shot.' She explained then to me basically just briefly what happened. And yeah, total shock obviously. So I had to jump in the car and rush through to Pretoria."

Van Zyl said he then called Ampie Louw, the sprinter's coach, and told him to jump in his car and get to Pistorius's house.

"When arrived at the house and you see all the police cars and lights ... I was standing outside, me and Peet and the lawyer, but Oscar was inside," Louw told CNN.

"I could hear him crying in the garage, and Reeva was at the entrance. So that was terrible for me."

Pistorius will make a brief appearance Tuesday at the Pretoria Magistrates Court, which will hear a motion by state prosecutors to postpone the case for further investigations. The trial itself may not happen until early 2014.