POLK COUNTY, Fla. -

An Aburndale man slapped and punched his 11-month-old stepson, hoping he would "wake up," said Polk County Sheriff's deputies. The child later died.

Edwin Cruz Vargas was arrested on Monday.

Vargas' wife left her baby, Josiah Figueroa, with Vargas, 25, for about an hour on Saturday, according to the arrest affidavit.

During that time, Vargas was trying to teach the baby to walk, became frustrated, and shook the child, said deputies.

He then tried to feed the baby a bottle of formula, but the baby wouldn't drink it. Vargas told detectives the formula began to pour out of the boy's nose, so he hit Josiah on the back., then called 911 and attempted CPR when the boy became unresponsive.

Vargas said while doing CPR, he slapped and punched the baby in an attempt to wake him, said deputies.

An autopsy revealed the baby suffered a broken lower back; a torn diaphragm near the spinal column, causing internal bleeding; 8 bruises to the top of the head; 2 bruises to the back of the head; and, a swollen brain. Dr. Vera Volnikh of the District 10 Medical Examiner's Office, who conducted the autopsy, ruled the baby died of blunt force trauma.

Vargas is charged with Aggravated Child Abuse and Negligent Manslaughter of a Child in connection with the death of the boy.

He was being booked into the Polk County Jail Monday evening.