Kyle Darren Halbauer, 23, was one of three people charged in the Sept. 12, 2012, death of Lorry Anne Santos in Saskatoon.
According to an agreed statement of facts entered in court, eight shots were fired at the home. Halbauer fired one shot that was nowhere near Santos, while an accomplice fired the rest, including the bullet that struck and killed her.
The statement said Halbauer and another accused were instructed to kill a former member of the White Boy Posse, an Alberta white supremacist gang they belonged to.
They were sent to a home in Saskatoon's Westview neighbourhood, but it turned out to be the wrong house.
The Santos family sobbed as Halbauer entered his guilty plea. His lawyer said he decided to admit to his role in the shooting after watching a video of the family.
"The reason his confession came about (was) the officer had showed my client a video of the victim's parents and a photograph of the victim," said defence lawyer George Combe.
"My client had lost his dad, who had died, and he lost one of his best friends to a car accident. That made him exceedingly remorseful.
"He wanted to take responsibility because he was — quote — 'an idiot' for doing what he did."
Crown prosecutor Matthew Miazga said the circumstances for the Santos family were especially sad.
"It's very heart-wrenching to listen to how people had something like this happen in their life purely by fluke," Miazga said outside the courthouse.
"Unfortunately the Santos family became victimized through this," added Saskatoon police Chief Clive Weighill.
"Fortunately we don't have many instances like this where you have some collateral damage when drug groups are battling each other."
Santos, 34, was on maternity leave from her job at the Saskatoon office of uranium mining giant Cameco.
She, her husband and children were awakened at 6:30 a.m. and she answered the door to strangers.
One of the woman's older children, a teenager, dialled 911. Santos was pronounced dead in hospital.
A conviction of first-degree murder comes with an automatic life sentence with no chance of parole for 25 years.
Combe said Halbauer, who was born in Lashburn, Sask., but moved to Lloydminster on the Alberta-Saskatchewan boundary, got in with the wrong crowd and became heavily involved in hard drugs after his mother experienced a debilitating stroke and his father died of a heart attack.
Halbauer decided to quit school and start work, a decision which led to his poor decisions, Combe said.
"(He) got into a group and did what he was told to do."
Prior to being sentenced, Halbauer's voice faltered as he addressed the Santos family in court.
"I'm sorry for changing your lives so drastically," he said, adding that if he could he'd "go back and walk away."
Two other men, Joshua David Petrin and James Wayne O'Hagan, also face charges of first-degree murder in Santos's death.