Three days before his daughter's killer was to be sentenced for a brutal, fatal beating, the man who found Christa Cachene's body at the bottom of her basement stairs died of a heart attack.

Leslie Whitehead passed away on Friday.

Sentencing arguments for Isaiah Rider, 20, who pleaded guilty earlier this year, began Monday morning.

"I would like to express my heartfelt sorrow to Miss Cachene's family; there's nothing I can say or do to take back what I've done," said Rider. "I'm here today to prepare myself to deal to the consequences."

Cachene's mother and sister walked out of the courtroom, refusing to listen to Rider's words.

The Crown prosecutor, Matthew Block, argued that Rider should go to prison for 18 years and serve at least half of his sentence before he's eligible for parole. Rider's lawyer Balfour Der proposed a 15-year prison term with the standard parole period. 

Der said his client suffers from fetal alcohol spectrum disorder (FASD), was passed from caregiver to caregiver and has lived a life filled with violence and substance abuse — all factors that, in his opinion, should be considered by the judge. 

"It's not surprising that a person may overreact like he did and resort to violence," said Der. "This is not a court without mercy."

Cachene, 26, was beaten so badly in October 2015 that her own father did not recognize her when he found her body.

In April, Rider pleaded guilty to manslaughter, four counts of assault and theft of a motor vehicle.

Isaiah Riel Rider

Isaiah Riel Rider pleaded guilty to manslaughter for the 2015 beating death of Christa Cachene. (Calgary Police Service)

Cachene was hosting a party at her home on the weekend of Oct. 9, 2015. The guests, which included Rider, partied on the Friday night and began drinking again Saturday morning. 

While friends were passed out around them on Saturday night, Cachene and Rider began to fight. Cachene used a small knife to stab Rider in the hand and lower back.

Then the two began punching each other. After he knocked Cachene to the ground, Rider began to stomp on her chest and head.

The struggle ended when Cachene was thrown down the basement stairs. Rider then used bleach to begin cleaning up his victim's blood. 

As he walked to a nearby C-Train station with friends the next morning, Rider confessed to killing Cachene. 

Cachene's injuries included a broken vertebrae, broken rib and perforated liver as well as considerable damage to her spine and neck and internal bleeding. She also was found to have a brain bleed.

Weeks later, after Calgary police issued an Alberta-wide warrant for Rider, he was on the side of Highway 2 after his car broke down near Ponoka. When a car carrying three people stopped to help, Rider beat all three with a baton. 

Rider will get three years credit for the time he has already served since his arrest. 

Court of Queen's Bench Justice Suzanne Bensler will deliver Rider's sentence next week.