DES MOINES, Iowa (AP) – Investigators say in a charging document that an 18-year-old who was involved in an ongoing gang dispute walked into the common area of an Iowa alternative education program for at-risk students and fatally shot two teenagers in a premeditated attack.

They say in the document released Tuesday that Preston Walls chased one of the teen victims down and shot him several more times when he tried to run.

The attack happened Monday at the Starts Right Here program in Des Moines. Police on Tuesday identified the victims as 18-year-old Gionni Dameron and 16-year-old Rashad Carr. Officers captured Walls leaving the scene. He is charged with two counts of first-degree murder and other crimes.