Nathaniel Kipi told police that he bottle-fed his 3-month-old son and put him down on the floor to sleep, then stepped outside to check on a teen brother when he heard the baby gasping.

The infant, Tama Wilbur, was taken to Kapiolani Medical Center where he died 31⁄2 weeks later on March 24, 2013.

An autopsy ruled the infant’s death a homicide caused by complications from “abusive head trauma.” Doctors said the lack of external injuries suggested that someone had injured the infant, possibly by shaking him.

Kipi, 24, of Makaha, was charged last weekend with second-degree murder in connection with the infant’s death. His bail is set at $150,000.

On Thursday, Family Court per diem Judge Wilson Loo found probable cause to charge Kipi with murder and sent his case to Circuit Court for a hearing later this month.

John Schum, Kipi’s attorney, said outside of court that numerous people had access to Wilbur and that the infant’s injuries could have occurred up to a week before his medical problems became apparent.

“Nate happened to be the one standing when the music stopped,” Schum said.

During the preliminary hearing, William Goodhue, who conducted the autopsy on Wilbur, said the infant had suffered bleeding on the brain and in his eyes. He said someone applied sufficient force to the baby, causing his brain to move and twist inside the skull, sheering nerve fibers and blood vessels.

Dr. Konstantine Xionis, the physician who first treated the infant at Kapiolani, said a battery of tests to determine whether a medical condition could have caused the baby’s condition came up negative. He said doctors suspected Wilbur was abused.

Kipi’s 16-year-old brother, who is not being named because he is a minor, testified he was in the room with Kipi and Wilbur just before the incident and didn’t see anyone hurt Wilbur. He said his brother was sitting next to the infant on the floor, trying to put him to sleep.

When the younger brother got up and walked down the hall, he heard Wilbur begin choking. He said he went back and saw the boy vomiting up milk and become “stiff.”

Kipi’s statement to police contradicted testimony from a neighbor’s sister, who gave the boy CPR until the ambulance came. A police sergeant testified that Kipi told her the baby had been sleeping inside for several hours before he began gasping.

Jocelyn Hanawahine, however, testified that she was visiting her sister next door and held Wilbur for about 10 minutes outside at a picnic table. He appeared to be acting normally, she said. Hanawahine also said Kipi went back inside with another son, a 10-month old, and one of Kipi’s younger brothers came out to pick up Wilbur and walked around the corner.

About a half-hour later, Kipi’s brothers began yelling for help because the baby was in distress. Hanawahine said she ran to Kipi’s house and found him at the front door holding the boy, who had no pulse.