ROSWELL, Ga. – A tragic story came to an abrupt end Wednesday when the man charged with the murders of two Roswell teens pleaded guilty but mentally ill for their killings.

Jeffrey Hazelwood was sentenced to life in prison without parole for the August 2016 murders of 17-year-olds Natalie Henderson and Carter Davis. The teen couple was found shot to death behind a Roswell Publix.

During the trial, psychiatrists testified that the now 21-year-old was hearing voices and thought people were monitoring his thoughts just weeks before the murders. Hazelwood also allegedly told those psychiatrists he was taking anti-psychotic, depression and anxiety medication just two days before the incident.

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A day after the brutal killings, Hazelwood was posting selfies on his Instagram account – a page that showed months of disturbing images. Those images included memes that read “love me or kill me” and “Your third face you never show anyone. It's the truest reflection of who you are.”

Attorneys cited Hazelwood's troubled past for his equally troubling actions that led him to eventually kill Henderson and Davis.

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Court documents showed that Hazelwood had been living with his grandparents for years after his mother was found unfit to be a parent. Attorneys said his mother was addicted to drugs and his grandparents stepped in to help raise him. They had sought psychiatric help for Hazelwood from a young age, and it was his grandparents who urged him to turn himself in for the murders.

Previously-released documents indicated Hazelwood had “severe behavior issues" and that police had been to Hazelwood’s Roswell home eight times since 2010. In one call, police were called after Hazelwood was suspected of stealing a gun. In another instance, police were called after a neighbor reported seeing Hazelwood swinging a sword and throwing knives in the front yard.

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Dr. Selig Cynman, Hazelwood's former doctor, testified during the trial that he treated him as a teen for three years and had met for approximately 82 sessions. During that time, Cynman said Hazelwood's symptoms included a fear of being spied on, a belief that there are cameras in his room, hearing voices, depressed mood, difficulty sustaining attention and difficulty sleeping.

Hazelwood told psychiatrists he had heard voices just days before killing Henderson and Davis and on the day of the murder, he followed the teens behind the Publix store. He climbed up to the roof of the grocery store and continued watching before confronting the two teenagers, who were in the backseat of Henderson's SUV.

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During the course of the trial, psychiatrists like Christian Hildreth, a forensic director for Central State Hospital, confirmed that Hazelwood suffered from psychosis, but that's not a mental illness. Hear Hildreth's description of Hazelwood's range of symptoms.

Hildreth said Hazelwood's medical team had not been able to pinpoint a mental health diagnosis for Hazelwood.

"We have struggled with putting a label on his mental illness,” he said. Although Hazelwood has a previous diagnosis of Asperger's disorder, Hildreth said “he never quite fit into the full spectrum of an autistic diagnosis.”

After his arrest, Hazelwood’s attorneys said he was not given his medication in jail. In a court hearing back in February, Hazelwood's appearance was shocking. At points during the proceedings, he seemed to shake uncontrollably in his handcuffs and appeared to pet an imaginary animal.

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But by April, attorneys said Hazelwood's medication was under control and he seemed much more resigned in court, with a clean-cut appearance and straightforward answers for the judge.

Before sentencing, Hazelwood's attorneys said he was deeply sorry for his actions: "He's very remorseful for what happened. He was off his meds when this happened and he was having hallucinations, audio and visual. He's very remorseful."

Hazelwood’s attorneys told 11Alive he pleaded guilty but mentally ill so that the state would have to continue treating him for his mental illness and he will remain under psychiatric care.

PHOTOS | Jeffrey Hazelwood