Police said the 2-month-old boy was in critical but stable condition, the Minneapolis Star Tribune reported.
Commander Catherine Johnson told reporters investigators know who the juvenile is and were urging him to turn himself in. Police had yet to find the gun involved in the shooting.
The newspaper said the baby's family initially told authorities the child had been the victim of random gunfire Thursday night as the father stood with him on a sidewalk outside a duplex, but investigators determined the father lied and that the boy's young uncle had accidentally fired the shot inside the home and then fled.
The names of the victim, the uncle and other members of the family had not been released.
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