A teenage boy has been sentenced to serve 25 to 50 years in prison for killing his 36-year-old mother in their Detroit home.

Joshua Smith was sentenced Friday in Wayne County Circuit Court.

His tearful grandmother spoke in court, saying she couldn't believe that the child she knew would commit such a crime.

“And I still want him to know that I still love him, I support him and I forgive him for anything for everything he did because that it was not him,” said Anne McKinzie. “I love you, Joshua.”

The 14-year-old shot and killed Tamiko Robinson as she slept on Feb. 27. Police say the shooting followed an argument.

Smith was charged as an adult and pleaded guilty to second-degree murder in September.

In a statement to police, Smith said he was tired of being called names. His stepfather's shotgun was used to kill Robinson.

Robinson's fiance, Chika Lewis, said he was sleeping in a back bedroom at about 3 a.m. when he heard several gunshots. He said he saw Smith holding his shotgun and that Robinson was "gasping for breaths."

He also testified that Smith pointed the gun at him and that he slipped when he stepped back, noticing it was from all the blood on the floor.

Lewis said he grabbed his 5-year-old daughter, broke out a kitchen window and ran for help to a neighbor's house.

Police say Smith then got into his mother's car and drove off. He was found a short time later and arrested.