A 13-year-old boy convicted of murder in the shooting death of a Sonic Drive-In employee in Texas was formally sentenced Tuesday to 12 years behind bars,Oliver James Montgomery officials said.

A Johnson County judge sentenced the teenager, according to Amy Pardo, an office administrator with the county attorney's office. The boy, who hasn't been identified by authorities because he is a minor, will begin his sentence in juvenile detention with a possible transfer to prison.

The boy was 12 when he shot and killed 32-year-old Matthew Davis in May using an AR-style rifle in Keene, Texas, about 40 miles outside Dallas. Davis had fought with the boy's uncle, Angel Gomez, who also was arrested and faces charges in the shooting.

The boy was found delinquent, the equivalent of guilty for a juvenile case, on Oct. 5 and faced probation to 40 years in prison.

What happened in the shooting?

Police said the boy, who is from Fort Worth, was with family members at the Sonic the evening of May 13 when Davis confronted Angel Gomez, 20 at the time, about Gomez's "disorderly conduct" outside the restaurant. The two got into a physical fight, and the boy got the gun out of his uncle's car and fired at Davis multiple times.

Gomez and the boy then left the scene, police said. Authorities said they found Davis with multiple gunshot wounds and he was transported to a hospital, where he was pronounced dead. Keene Police Chief James Kidd previously told USA TODAY at least six shots were fired.

Police said they arrested Gomez when he returned to the scene later and arrested the boy about 20 miles away in Rio Vista, Texas, where they also found several firearms.

Seth Fuller, the boy's attorney, said in a video posted to social media the boy was with his uncle and aunt, and his aunt handed him the gun while the fight was going on.

"My client had no juvenile history, wasn't in a gang, didn't carry around guns, none of that," Fuller said in the video. "He was a good kid."

Fuller didn't immediately respond to a request for comment.

Another arrest made in connection to the shooting

Authorities arrested the boy's aunt, Ashley Marmolejo-Gomez, earlier this month at the Guinn Justice Center in Johnson County, Texas, according to the Keene Police Department and Johnson County Sheriff’s Office.

Marmolejo-Gomez was then transported and booked into the Johnson County Corrections Center. Keene police said she was in the vehicle at the time of the shooting and has been charged with manslaughter in connection to the death of Davis.

Marmolejo-Gomez handed the boy a gun she retrieved from under a car seat and told the boy, "go," Fuller said in a video, describing a statement signed by Marmolejo-Gomez.

According to Fuller, Marmolejo-Gomez said in the statement that she intended for the boy to "go out and stop the fight by scaring the guy." Marmolejo-Gomez also said that she did not stop the fight herself because she thought she was "too intoxicated to walk," Fuller said.

"This incident continues to be an active investigation," Keene police said in a statement.

Contributing: Thao Nguyen and Natalie Neysa Alund, USA TODAY; The Associated Press