The autopsy showed that Mansour Ball-Bey, 18, died from a single bullet that struck his upper right back and hit his heart and an adjoining artery, St. Louis Chief Medical Examiner Michael Graham told Reuters on Friday. The bullet did not exit Ball-Bey’s body, and killed him “nearly instantly.”

Ball-Bey was African-American. Both officers involved in the shooting are white. Some 150 protesters gathered at the scene on Wednesday evening. When police tried to disperse them, the protesters threw rocks and bottles. Police responded with tear gas. A car and a house were set on fire, and nine protesters were arrested.