An additional arrest has been made in the investigation into the death of a 6-month-old Tucson boy.
The mother of 6-month-old Killian MacDonald, 31-year-old Tamara Fowler was arrested and booked into the Pima County jail.
Killian's father, 22-year-old Zechariah MacDonald, was arrested in February.
According to Tucson Police, Tamara had known Zechariah would use blankets and other items to cover the babies face to muffle noise.
Police say the charges against Zechariah were amended to one count of first-degree murder and three counts of child abuse.