BLACKFOOT — A Blackfoot man accused of killing an 18-month-old boy has pleaded guilty to first-degree murder.

Jesus Adan Castillo, 22, was charged with murder after prosecutors said he struck Zachary Tendoy, the son of Castillo’s girlfriend, in the head and abdominal region earlier this year. The injuries Zachary sustained in the attack led to his death on March 25.

The attack occurred at a residence in the 1600 block of Camas Street in Blackfoot. When police and paramedics arrived on scene at approximately 4 a.m. on March 23, they found Zachary, who was unresponsive and lying limp on the floor.

After Zachary was transported to Bingham Memorial Hospital, court documents state that doctors discovered numerous traumatic injuries, including multiple skull fractures, swelling of the brain, major blood vessel tears and retinal hemorrhaging. A court document said that to sustain similar injuries, a child similar in size to Zachary would have to be in a 70 mph car accident.

Zachary later died from his injuries at 2:47 p.m. on March 25.

According to court records, Castillo told investigators that he “heel-kicked” the boy in the stomach. He also admitted to shaking Zachary multiple times and hitting him as hard as he could before authorities arrived at the residence on Camas Street.

Castillo was initially arrested and charged with felony aggravated battery and felony injury to a child. After Zachary’s death, the charges were amended to first-degree murder. Castillo initially pleaded not guilty to the murder charge in May, but later changed his plea.

The case was investigated by the Bingham County Sheriff’s Office and the Blackfoot Police Department.

Castillo will be sentenced on Jan. 22, 2018, at 3 p.m. before Seventh District Judge Dane Watkins. Castillo faces 10 years to life in prison.