Tucson police detectives continued investigation has led to a second arrest after the death of a 6-month-old child on Feb. 8.

The child's mother, 31-year-old Tamara Fowler, was arrested without incident and charged with first-degree murder and three counts of child abuse, the department said Friday. 

Officers first arrested 22-year-old Zechariah MacDonald, the father of the child, in connection with the death on the day of the incident. The charges against him have been amended from domestic violence-related manslaughter to first-degree murder and three counts of child abuse after the case was presented to the Pima County Attorney's Office.

Shortly before 6 p.m. on Feb. 8, police and paramedics went to an apartment at 520 West Prince Road for reports of an unconscious child who wasn't breathing, Sgt. Pete Dugan, a Tucson Police Department spokesman, wrote in a news release.

Paramedics with Tucson Fire Department began first aid and took the child, who had life-threatening injuries, to Banner University Medical Center.

Shortly after arriving at the hospital, the baby was pronounced deceased, Dugan said.

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TPD detectives took over the investigation and learned through evidence at the scene and interviews with the MacDonald, that he was alone with his two children while their mother was at work. At some point during the afternoon, MacDonald put Killian, the 6-month old, in a playpen and went to take a nap, Dugan said.

Because Killian was crying, MacDonald put multiple blankets over the baby's body to muffle the noise. When MacDonald woke up several hours later, he found Killian unresponsive, Dugan said. 

Detectives from the child abuse unit learned Fowler had known MacDonald would use blankets and other items to muffle the baby's noises, leading to her arrest.

Both parents were booked into the Pima County Jail.

Contact reporter Caitlin Schmidt at cschmidt@tucson.com or 573-4191