An investigation into Yanis began in November. The details of the plot were released in early December.
Prosecutors say he planned to kill students who had picked on him at /*Pottstown Senior High*/.
He then intended to take his own life.
In exchange for the admission to attempted murder, the other charges against Yanis will be dropped and the case will stay in juvenile court.
Yanis will now spend 6 years in a secure psychological treatment facility.
District Attorney Risa Vetri Furman said Wednesday that Yanis stole three guns from his father back in November, and gave them to a friend to hold.
Furman said that friend then gave the guns to his step-mother, 51-year-old Julie Ann Macedo.
Macedo allegedly threw the guns in a creek, and repeatedly lied to police about the case.
She faces charges of tampering with evidence and reckless endangerment.
Macedo is expected to surrender to police tomorrow.
Her step-son, Yanis' friend, faces juvenile charges.
