An Indiana teenager is set to face adult charges in connection with the tragic double homicide of his father and great-uncle, following a series of alarming threats he allegedly made against his family.

Fifteen-year-old Jeremiah Nicholas Dill has been named by authorities as the suspect in the fatal shootings of his father, 41-year-old Grantham Chandler, and his great-uncle, 61-year-old Jeffrey Fauber. The two men were discovered shot dead in a driveway in Quincy, Indiana, on August 9. Shortly after the incident, a woman at the scene contacted 911, and Dill reportedly turned himself in at the Morgan County Jail, admitting to the alleged crimes.

Court documents obtained by WXIN, a local Fox affiliate, reveal that the 911 caller identified the alleged shooter as a “15-year-old boy who just got released” from inpatient mental health care. Earlier in the year, Dill had been admitted to a mental health facility after making threats against his family, including a specific threat to kill his father and knowledge of where the firearms in the house were stored.

According to police, Dill was discharged from the facility just two days prior to the shooting. Despite family members’ efforts to secure all firearms in the home, Dill managed to gain access to them. The woman who contacted 911 reported that after the shooting, Dill fled the scene in the family’s Ford Escape, taking several guns with him.

Upon arriving at the jail, Dill allegedly made several incriminating statements, such as “I killed my father” and “I killed my family,” and declared he was “fighting demons.” While in custody, Dill continued to speak, reportedly informing officers, “The guns that I killed him with are in that car,” referring to the Ford Escape mentioned in the 911 call.

Investigators searching the vehicle discovered an AR-15 rifle and a handgun, adding to the mounting evidence in the case.

According to court documents, a woman at the home where the shooting took place told police that Dill had been acting “chill” and “uncharacteristically helpful” that morning. He also allegedly made statements that he wanted to “kill the family.”

Dill will be charged as an adult with two counts of murder. He is currently being held in juvenile custody, according to local NBC affiliate WTHR. His next court date is scheduled for Dec. 11.