A 24-year-old Atlanta man will spend the rest of his life in prison for the execution-style killing of a friend in 2017, the Cobb County District Attorney’s Office said.

On Oct. 14, 2017, Corey Nelson went to the Austell home of Khristopher Dixon with a gun, according to investigators. Dixon allowed Nelson in, unaware of his motives. Moments later, Nelson shot Dixon in the back of the head with a .380-caliber handgun, prosecutors said.

Nelson then went downstairs and back upstairs, where he fired two more rounds into Dixon’s head, the DA’s Office said. A neighbor heard tires squealing as Nelson sped out of the neighborhood in a dark SUV before police arrived.

Dixon died from his injuries. He was 22.

“This was, by all definitions, a senseless killing. Khris Dixon was a good kid with a promising future ahead,” Senior Assistant District Attorney Stephanie Green said in an emailed statement. “He was extremely motivated and artistic, working hard to make his family proud.”

The day after killing Dixon, Nelson was arrested and charged with murder. Investigators identified Nelson as the shooter through Instagram messages from Nelson to Dixon saying “I’m here” minutes before the shooting.

Detectives found the murder weapon at Nelson’s home along with his cellphone, the DA’s Office said. On his phone, Nelson had a photo of Dixon after being killed.

No motive for the killing was determined. On Oct. 27, Nelson pleaded guilty and was sentenced to life in prison. He is serving his time at the Georgia Diagnostic and Classification State Prison in Butts County.