Police said the shooting happened in Minneapolis's Riverside neighborhood on the 1900 block of 7th Street South. They were called to the scene just before 1 p.m.
Both reports say the toddler was pronounced dead in the ambulance at the scene.
Minneapolis Police Sgt. William Palmer says the the toddler was shot by his 4-year-old brother who was playing with a fire arm.
Palmer says the parents and their 1-year-old were also home at the time of the incident. They also have a 5-year-old, who was not home at the time. Their children are in protective custody for the time being
There have been no arrests, but the parents are being interviewed by investigators, according to both reports.