A 16-year-old boy accused of planning a mass shooting at Hilliard Davidson High School was released from detention April 17 by a Franklin County judge who placed him in his mother's custody with an electronic monitoring device while the case is pending.

Juvenile Court Judge Terri Jamison made the ruling after John L. Staley III admitted that prosecutors have enough evidence to establish probable cause, or a reasonable belief, that he committed conspiracy to commit murder.

The next step in the process is a May 25 hearing at which Jamison is expected to decide whether Staley, who lives in northwest Columbus, would respond to treatment within the juvenile system or should be transferred to adult court.

Assistant Prosecutor Joseph Gibson said his office "vehemently" opposed Staley's release from detention after giving the judge a detailed review of the shooting plans, which included diagrams of the school and efforts to recruit other students.

Gibson also revealed that investigators uncovered online chats in which Staley used "horrifically racist language, particularly aimed at African Americans and Jewish people," which might point to his motivation.

"All of that happened under the supervision of his parents," Gibson said. "I don't believe that releasing him back to that environment makes any of us safer. He was far along in carrying out an attack on a school."

Jamison said Staley has no previous delinquency record, would be eligible for bail if he were an adult, and must be confined to his mother's house unless making approved trips to see his attorney, psychologist or probation officer.

Staley, who spoke briefly when asked by the judge if he understood the proceedings, showed no emotion until the end of the hearing, when he and his mother cried as they embraced.

Staley was arrested in October after police became aware of plotting that they say had begun the previous school year. He was a sophomore at Davidson when another student overheard him discussing the plot on a school bus and alerted a school resource officer.

Investigators determined that Staley began trying to recruit classmates to help him in spring 2016, Gibson said.

Two of those students "feigned interest" in helping with the plot. One has been charged with a delinquency count of tampering with evidence for destroying one of Staley's diagrams.

Searches of Staley's computer, school-issued iPad and cellphone showed that he searched topics such as Oklahoma City bomber Timothy McVeigh, the Irish Republican Army and how to purchase firearms, Gibson said.

The searches also turned up "extremely disturbing ... photos of Nazi and neo-Nazi imagery" and "images glorifying school shootings and making light of the Holocaust," he said.

The diagrams Staley created focused on the school's common area and auditorium and listed the ammunition and guns needed for the attack, as well as the names of the two students responsible for the Columbine High School massacre, Gibson said.

Investigators found four gas masks and a tactical vest in a search of the house where Staley lived with his mother.

Defense attorney Steve Palmer said much of what Gibson recited will be in dispute when his client's case is presented.

"Should this case, and when this case, proceeds to trial, hopefully in (juvenile) court, we will take issue with lots of those facts, in particular what the government's beliefs are about those facts," he said.