Authorities in Kentucky say a teenager accused of fatally shooting two high school classmates and wounding several others showed no remorse when talking about the carnage.
Police say Gabriel Ross Parker seemed to view his actions as a science experiment.
Parker has been charged as an adult in the January 23 shooting at Marshall County High School in western Kentucky. Media reports this week cite court documents and videos released after the case was moved to adult court. Parker turned 16 after the shooting.
Marshall County Sheriff's Captain Matt Hilbrecht testified that Parker told police he was interested in science and wanted to see how people would react.
"He said he wanted to see how students would respond, how police would respond, how society at large would respond to it," said Hilbrecht.
He described Parker as "cold, callous" and said he showed no emotion during the interview."
His voice never quivered, never had any inflection," the detective said. "He didn't tear up."
Parker told police that he wasn't bullied and that no event triggered the shootings.
Asked about Parker's motives, Hilbrecht said, "The biggest thing he gave me was that he said he was an atheist and that his life had no purpose and other people's lives also had no purpose."
Kentucky State Police Detective David Dick testified that the boy contemplated shooting himself in December, "but realised that his family would hurt more if he killed himself, rather than if he just went to prison for harming someone else."
Hilbrecht testified that Parker, who played trombone, went to the band room on January 23 to make sure his friends were safe before going to a common area where he began firing. When he was done, according to Hilbrecht, he returned to the band room and blended in with students before surrendering to police.
The next hearing in the case is set for Monday.