A school shooter who killed two students and two teachers in Georgia has pleaded guilty to 55 counts.

Colt Gray, 16, entered the plea Friday without having reached a deal with prosecutors. He had previously pleaded not guilty to charges in the Sept. 4, 2024, shooting at Apalachee High School that killed four people and left several others wounded about 45 miles (73 kilometers) northeast of Atlanta.

Barrow County Superior Court Judge Nicholas Primm is now set to hear each side’s summary of the case, evidence and sentencing recommendation before deciding the sentence.

Gray’s trial had been scheduled to start in mid-October in Columbia County, about 100 miles (160 kilometers) from where the shooting happened, after the judge agreed to a defense request for a change of venue.

A jury in March convicted his father, Colin Gray, on charges including second-degree murder and involuntary manslaughter, and he is scheduled to be sentenced next week. Prosecutors said the elder Gray gave his son the assault-style rifle used to open fire at the school.

Teachers Richard “Ricky” Aspinwall, 39, and Cristina Irimie, 53, and students Mason Schermerhorn and Christian Angulo, both 14, died in the shooting. Another teacher and eight more students were wounded, seven of them hit by gunfire.

Gray’s defense attorney wrote in a court filing that he plans to call a psychologist, a counselor at the juvenile detention center where he has been held and his grandmother to testify.

Gray, who was 14 at the time of the shooting, was charged as an adult with 55 total counts, including murder in the four deaths and 25 counts of aggravated assault.

Investigators testified that the teenager carried the rifle onto the school bus with the barrel wrapped in a poster board. They said he left his second-period class and emerged from a bathroom with the rifle, shooting people in a classroom and hallway.

Investigators have said Colt Gray carefully plotted the shooting at the high school of 1,900 students. A Georgia Bureau of Investigation agent testified that the teen left a notebook in his classroom with step-by-step instructions and a diagram to prepare for the assault, including an estimate that he could kill as many as 26 people and wound as many as 13 others.

Sheriff’s deputies interviewed Colt and Colin Gray in May 2023 about an online threat linked to the son. Colt Gray denied making the threat. He skipped eighth grade, enrolled as a freshman at Apalachee after the academic year had begun and then had a spotty attendance record.

Investigators found a shrine in Colt Gray’s bedroom to Nikolas Cruz, the shooter in the 2018 massacre at Florida’s Marjory Stoneman Douglas High School, prosecutors said.

An investigator testified during Colin Gray’s trial that he had been aware that his son’s mental health had deteriorated and sought help from a counseling service weeks before the shooting, citing anger, anxiety and volatility. But the father never followed through on getting help for his son, the investigator said.

His mother, Marcee Gray, who was separated from Colin Gray, told investigators she had urged him weeks before the shooting to secure his guns and restrict their son’s access to them. Instead, over time, Colin Gray bought the boy ammunition, a gun sight and other shooting accessories, records show.