Emotions exploded in a violent, dramatic scene in a Calgary courtroom on Wednesday as the man who killed Christa Cachene was attacked by her best friend immediately after being sentenced to 15 years in prison.

Only one sheriff was in the courtroom, guarding Isaiah Rider, as the attacker stormed the prisoner's box yelling "your court is a f**king joke."

She got between the two, fending off the attacker, who was identified only as "Josh" by Cachene's mother. In one motion, the sheriff pulled her baton while shoving Rider into the back cells. She radioed for backup.

"The sheriff did a fantastic job," said Rider's lawyer, Balfour Der. "This was a highly volatile situation."

Outside the courtroom, sheriffs arrived and arrested the man for assault, taking him to the basement cells of the courthouse. Members of Rider's family who were in the courtroom were taken to the cafeteria to write out witness statements.

"I'm sick to my stomach, I'm worried about his life in jail," said Rider's mother, Amanda Kayseas, who was shaking and crying after giving her witness statement.

Calgary police confirmed they have a man in his early 30s in custody who is facing charges of assault and assaulting a peace officer.

Court of Queen's Bench Justice Suzanne Bensler had just left the courtroom when the outburst occurred.

"Never seen that before," said prosecutor Matthew Block. "Emotions were obviously high. It's obviously not the right way to go about it."

Nancy Cachene says she's unhappy with the 15-year sentence her daughter's killer was handed Wednesday. (Meghan Grant/CBC)

Prosecutors Joe Mercier and Block had proposed an 18-year sentence and that Rider serve at least half of that before being eligible for parole. Rider's lawyer proposed a 15-year prison term.

"No sentence can reflect the value of [Cachene's] life," said Bensler before ruling that Rider would be able to apply for parole after the standard one-third of his sentence.

But Cachene's family members were disappointed with the prison term.

"It is never going to be enough because she's not coming back," said the victim's mother, Nancy Cachene. "She's never going to come back."

In October 2015, Cachene's father arrived at her home to drop off the 26-year-old woman's children. When Leslie Whitehead found his daughter's body at the bottom of her basement stairs, he didn't recognize her because she had been so badly beaten.

Whitehead died less than two weeks ago, before he could see his daughter's killer sentenced.

Originally charged with second-degree murder, Rider pleaded guilty to manslaughter in April.

Cachene was hosting a party at her home over the weekend of Oct. 9, 2015. On the Saturday night, Cachene used a small knife to stab Rider in the hand and lower back after a fight broke out between the two. Rider then knocked Cachene to the ground and began to stomp on her chest and head.

Eventually, he threw her down the basement stairs. An autopsy would find Cachene suffered a broken vertebrae, broken rib and perforated liver as well as considerable damage to her spine and neck and internal bleeding.

After Calgary police issued an Alberta-wide warrant for Rider weeks later, the fugitive found himself stranded with a broken-down car on the side of Highway 2. When passersby stopped to help, Rider beat them with a baton. He pleaded guilty to assault and theft of a motor vehicle.

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

Isaiah Rider's sister and mother are embraced after he was sentenced to 15 years in prison for killing Christa Cachene in 2015. The family was shaken after Rider was attacked in court by Cachene's best friend. (Meghan Grant/CBC)

Kayseas said her son is loved and feels remorse. Both she and her own mother, Karen Desjarlais, spoke of the intergenerational trauma suffered by their family's four generations of residential school survivors.

Desjarlais said she had a "lack of parenting skills," which she passed on to her daughter.

"There was a lot of addictions that ruined, that had a great impact on how I brought up my girl and how she brought up her son," said Desjarlais.

His family hopes Cachene's are in the process of healing.

"We want them to understand we feel their loss. We are so sorry, and there's nothing that can change this other than to forgive, heal and grow."