Police Chief Edward Flynn told reporters Monday the 18-year-old man has 15 previous arrests. He was on probation for burglary when Sierra Guyton was shot in the head and seriously wounded Wednesday night. Sierra remains hospitalized in critical condition.
Police say the girl was caught in the crossfire at the Clarke Street Elementary School playground between two people shooting at each other.
Flynn says the suspect's arrest record includes battery, robbery, vehicle theft, trespassing and burglary.
A second suspect remains at large.
Mayor Tom Barrett is urging the people of Milwaukee to put down their guns.
Flynn says they need the community to stay "engaged and enraged."