One of Reeva Steenkamp's relatives gave a moving testimony during Oscar Pistorius' sentencing hearing on Tuesday about the late model who was killed last year.

Pistorius, a famed Paralympic athlete nicknamed the "Blade Runner," fatally shot Steenkamp on Feb. 14, 2013. The Olympic champ pleaded not guilty to first degree murder, arguing that he shot her by mistake because he thought she was an intruder in his home. However, prosecutors in the high profile case claimed that he killed her out of rage after the couple had an argument in the wee hours of Valentine's Day.

Last month, Judge Thokozile Matilda Masipa found Pistorius not guilty of first degree murder, but guilty of culpable homicide, a lesser charge also known as manslaughter, which is punishable with up to 15 years in prison, reports Fox News.

On Tuesday, Kim Martin, who was the first of Steenkamp's family members to give testimony, said that her world ended when she found out on a car radio that the 29-year-old model had been fatally shot.

"I was trying to phone her (Reeva) and she wasn't answering and I was screaming at my husband," Martin recalled, according to the Associated Press.

Martin, who was Steenkamp's cousin, said she got confirmation that the dreadful news was true when she went to her mother's home and found her mother crying uncontrollably.

"The doors opened and my mother was hysterical and that's when I knew it was true. That was for me the end of the world. Everything was just a blur from then onwards."

Her emotional testimony caused the judge to stop for a brief adjournment when she began crying on the stand.

"We were all, 'why, why, why Reeva?'" Martin said. She said Steenkamp's killing "ruined our whole family."

Steenkamp's parents, Barry and June, decided they were too emotional to testify.

According to Martin, Steenkamp's mother June was on medication after the killing while her father sat in a corner of his house crying. She also said that she is receiving trauma counseling and her children need therapy.

The tragedy "ruined our whole family," she said. "It's ruined uncle Barry and auntie June. Reeva was everything to them. She was their only child in PE [Port Elizabeth] for a long time and they absolutely adored her. They were so proud of her, what she'd accomplished. She looked after them so well, not just financially," she said, according to The Guardian.

Pistorius' sentencing phase is expected to last for most of the week. Judge Thokozile Masipa will then issue a sentence, which can range from a hefty fine to over a decade behind bars.