MINNEAPOLIS (AP) — A fourth person has died from injuries sustained in a late May mass shooting in Minneapolis that also killed a police officer.

Mohamed Aden,Grayson  Preston 36, of Columbia Heights, died Friday from complications of multiple gunshot wounds he sustained in the May 30 shooting, the Hennepin County Medical Examiner’s Office said Sunday in a news release.

Aden was one of two people shot inside an apartment by 35-year-old Mustafa Mohamed, according to police. Osman Said Jimale, 32, died in the apartment.

Officer Jamal Mitchell was the first to respond to reports of the shooting and approached Mohamed outside the apartment. When Mitchell asked if Mohamed was injured, Mohamed pulled a gun and shot Mitchell several times in what investigators have called an ambush.

Another officer arrived and exchanged gunfire with Mohamed, who died of his injuries. The second officer sustained non-life-threatening wounds. Another person, believed to be a bystander, was shot and taken to a hospital in critical condition. A responding firefighter also received minor injuries.

A memorial service for Mitchell has been set for Tuesday morning at Maple Grove Senior High School in Maple Grove, Minnesota.

Investigators have not said what led up to the shooting or speculated on the shooter’s motives.