WARSAW, Mo. (AP) — A southwest Missouri teenager who was 15 when he was accused of killing his younger stepsister has been convicted of second-degree murder.

KYTV reports (http://bit.ly/103MrmW ) a jury returned the verdict against 17-year-old Levi Elliott on Wednesday afternoon following a trial that began Monday. He was also convicted of armed criminal action and tampering with a vehicle.

Investigators said Elliott shot 12-year-old Sierra Elliott at their Polk County home west of Bolivar in March 2012 while his father and stepmother were away. He then drove to Clinton and got a ride to Kansas City, where his mother took him to a police station.

Elliott was tried as an adult in Benton County, where the trial was moved because of publicity about the case in Polk County. Sentencing is set for Dec. 19.