BOISE, Idaho (AP) — The lead prosecutor tasked with finding justice for four University of Idaho students killed in a grisly quadruple stabbing more than two years ago laid out his key evidence Wednesday at a court hearing for Bryan Kohberger, who agreed to plead guilty earlier this week to avoid the death penalty.

Bryan Kohberger appeared expressionless as a judge asked if he murdered four Idaho college students in their off-campus home, answering “yes” to each name called out in the courtroom Wednesday.

With a series of “yes” replies to a judge, a man accused of killing four Idaho college students pleaded guilty in exchange for life in prison and no death penalty. But left untold so far: What motivated Bryan Kohberger to commit the middle-of-the-night knife attacks and why those victims?