TUCSON, Ariz. - A man has been arrested in connection with the homicide of his 6-month-old son.

Firefighters responded to an apartment near Prince and Oracle roads Thursday for a report of an unconscious child who was not breathing.

The child was taken to Banner University Medical Center with life threatening injuries and was pronounced dead shortly after arriving.

The 6-month-old was identified as Killian MacDonald.

Police said Killian's father, 22-year-old Zechariah MacDonald, was home alone with his two children — Killian and a 2-year-old daughter — while their mother was at work.

At some point in the afternoon, Zechariah wanted to take a nap and placed Killian in a playpen, police said.

According to police, he placed multiple blankets over his body to muffle the child's crying. Several hours later, Zechariah woke up and found Killian unresponsive.

Detectives booked Zechariah into the Pima County Jail. He faces charges of domestic violence and manslaughter.