UPDATE: Stabbing Victim Was Murrieta Valley High School Senior

An 18-year-old stabbing victim killed this morning in her Murrieta home was confirmed tonight to be Saskia Burke, a senior at Murrieta Valley High School.

Catherine Burke, the girl's mother, identified her daughter to Patch in a tear-filled interview.

Burke's suspected killer, 19-year-old William Gary Simpson, is still at large. to read more about the Murrieta Police Department's search for him.

To read about the circumstances of Burke's murder and its aftermath, .

'She died in pain'

Catherine said she rushed to save her daughter from her killer but was too late.

"She died in pain," the mother said. "She died screaming for us to help her, and by the time we got there he'd already murdered her."

Simpson fatally wounded Saskia before attacking the girl's 17-year-old boyfriend and 48-year-old father, Catherine said. The two underwent surgery at local hospitals and were still in critical condition on Tuesday, according to police.

The Burke family took Simpson in after he left his parents home, but the suspected killer was asked to leave the home a year ago, officials said.

Catherine described the teenage suspect as "selfish and arrogant."

"I'm sorry that when I took the knife away last night I didn't kill him with it," she said.

The family will be forever scarred by the loss of their daughter, the mother said.

"I loved her so," Catherine said. "I don't know how to go even one moment. I don't know how to go without her."

The Burkes asked for help in finding their small white terrier, named Archie, who has been missing since this morning.

The dog may be covered in blood, Catherine said.

Editor's Note: Conflicting law enforcement reports gave different ages for the deceased female victim, Saskia Burke. Her age has been changed in the story to 18-years-old per a Riverside County Sheriff-Coroner report.