LAKELAND, Fla. -- A Lakeland man was arrested Thursday on murder charges in the death of his 5-month-old daughter after his 5-year-old son demonstrated for detectives how he slammed the girl's head into her crib, deputies said.

Timothy King, 31, was arrested on first-degree murder charges in the death of his daughter, Kyra.

According to the Polk County Sheriff's Office, King called 911 on July 9 to report that his baby girl was not breathing and had mucus coming out of her mouth.

A Polk County deputy sheriff performed CPR on the baby and was able to resuscitate her, and she was transferred to St. Joseph's Children's Hospital in Tampa, deputies said.

Medical test results showed that Kyra had several hemorrhages inside her head, bruising to her head and lower back and old fractures on her left arm that had gone unreported and untreated, deputies said. She had no brain activity and was being kept alive by life support, which was disconnected on July 10, according to the Polk County Sheriff's Office.

An autopsy showed the bruises resulted from at least four and possibly more separate strikes from a blunt force object, according to the medical examiner, who ruled the cause of Kyra's death to be blunt impact with subdural and subarachnoid hemorrhages and the manner of death to be homicide.

Detectives interviewed Kyra's 5-year-old brother on Monday, and he said that he saw his father slam Kyra's head into the crib, according to the sheriff's office. The detectives asked the boy to demonstrate the actions with a doll, and he slammed it head-first onto the ground two times, deputies said. When the detectives asked the little boy when Timothy did this to Kyra, he replied, "The other day," according to the sheriff's office.

"This baby suffered significant pain for at least the last three or four weeks of her life when the bones in her arm were broken. It is inconceivable to me how anyone could inflict that kind of injury on a baby, much less how anyone could beat this beautiful baby to death the way Timothy King did," Polk County Sheriff Grady Judd said. "Now he is behind bars where he belongs, where he cannot hurt any more children."