Officers respond to a call about a shooting at the downtown apartment complex around 11:35 p.m. when they made the grim discovery.
Emergency responders immediately started performing CPR and transferred the boy to a local hospital, where he later died.
"We have two juveniles alone in a residence with access to a gun, and that is always a bad recipe," Minneapolis Police Department spokesperson Garrett Parten said at a news conference Saturday.
The Hennepin County Medical Examiner will perform an autopsy and determine the child's exact cause of death before identifying the boy.
Police have not released the age of the other juvenile who was home at the time of the shooting.
The Minneapolis Police Department is now urging the public to secure their guns in the wake of the shooting.
"We are asking that any gun owner or anybody who has weapons in their homes to please take every measure necessary to secure their weapons," Parten said.
"That would include things like trigger locks and securing these weapons in a containment unit that is locked and not easy to get open, something like a gun safe."
So far this year, 88 children and 371 teens have been killed by firearms, according to the non-profit Gun Violence Archive.