Chance Harmon, now 20 years old, was sentenced to 20 to 40 years in state prison.
Harmon killed 16-year-old Anthony Ross.
The judge said Harmon presents "a continuing danger to the community."
The victim's mother, Lakia Jackson, described her son as a "ray of sunshine" who had big plans.
"All he wanted to do is become a SWAT team member. He said he was going to clean up the streets. He never got a chance to do that," Jackson said.
In court, Jackson told Harmon she prays for him every day to understand the consequences of his actions.
