Police say narcotics were involved in both cases.
A third shooting victim is in critical condition at a the hospital.
St. Louis police are investigating after several cars were damaged by rocks thrown from a railroad overpass.
Prosecutors allege Carl Kelley shot three people in October. One, 38-year-old Byron Gallion, died.
In St. Louis, between 10,000 and 15,000 federal workers are being affected by the government shutdown and some plan to protest today.
Tuesday evening, five people were sitting outside a home in the 1800 block of Switzer when someone in a dark-colored car with tinted windows drove by and opened fire.
Around 3:30 a.m., a black SUV arrived at the north patrol headquarters for St. Louis Police on Goodfellow. Inside police found the child unconscious with a gunshot wound to the head.
Two happened in north St. Louis County and the other in north St. Louis. Investigators are trying to determine if they were pulled off by the same criminals.
Prosecutors say 65-year-old Leronald Loper, an employee of the Corps, planned to rob an armored car.
Suspect’s car may be a white Impala with a spotlight on the driver’s side.