Police say 21-year-old Megan Sherrard of Calais is in critical condition at the Eastern Maine Medical Centre in Bangor after being shot twice in the chest.
Her son, Luca, is expected to recover after being grazed by a bullet.
Around 6pm last night, Calais Police Department recieved a call of shots fired at a home at 417 Main Street.
Police say shortly after arriving on scene, police shot and killed 26-year-old Daniel Pinney, who is the baby's father, and who is believed to have shot the baby and Sherrard.
Police say Calais PD veteran officer John Preston was also grazed by a bullet during the incident and is expected to recover.
The Maine Attorney General's Office is investigating whether "deadly force" used by police was justified.
An employee from Bells IGA tells Tide News Sherrard was a cashier at the store in Calais and Pinney was a bagboy.
