The sister of one of the four University of Idaho students slain in their off-campus home blasted the “shocking and cruel” plea deal that will spare the life of accused killer Brian Kohberger.

Aubrie Goncalves, 18, voiced her outrage over the deal in which Kohberger will cop to killing her sister Kaylee Goncalves and three others, in a lengthy statement posted on Facebook.

“The introduction of this plea deal, just weeks before the scheduled trial, is both shocking and cruel,” Aubrie wrote.

“We’ve had faith in the system. But at this point, it is impossible not to acknowledge the truth: the system has failed these four innocent victims and their families,” she continued.

State prosecutors reportedly sent a letter to the families of the murdered students informing them of the deal that will let Kohberger dodge the death penalty — provided he admits to breaking into a student rental and butchering four University of Idaho undergrads in 2022.

The deal waives Kohberger’s right to appeal and demands a life sentence without the possibility of parole, according to the Idaho Statesman.

But for Aubrie, a lifetime behind bars isn’t enough for her sister’s death.

“Bryan Kohberger facing a life in prison means he would still get to speak, form relationships, and engage with the world,” Aubrie wrote. “Time and time again, we find ourselves blindsided, unheard, and unsupported. This last-minute plea deal feels less like an act of justice and more like an afterthought.”

Kohberger, a PhD criminology student, is facing four murder charges for allegedly breaking into a house near the University of Idaho in the middle of the night and fatally stabbing Ethan Chapin, Xana Kernodle, Madison Mogen and Kaylee Goncalves.

Prosecutors recently revealed they obtained evidence that Kohberger, in the months before the killings, purchased a knife and knife sheath online, CBS News reported.

And Kohberger reportedly left DNA on a knife sheath found at the crime scene, according to a police affidavit.

But Kohberger, a clean-cut doctoral student at the nearby University of Washington during the time of the attacks, had previously claimed he was totally innocent of the quadruple homicide that rocked the nation.

His lawyers had pushed for delays to the trial and sought to keep the most damning evidence out of the courtroom, including surveillance videotape and DNA collected at the crime scene.

Aubrie wrote that the ceaseless delays and procedural hangups have “placed heavy burdens on those already carrying unimaginable grief.”

Yet prosecutors insisted that the plea deal was the best path to justice.

“This agreement ensures that the defendant will be convicted, will spend the rest of his life in prison, and will not be able to put you and the other families through the uncertainty of decades of post-conviction appeals,” read the letter obtained by the Statesman.