Editor's note: This article contains details that some readers may find disturbing. Discretion is advised. SALT LAKE CITY — A teenager accused of killing his girlfriend's young son has been charged as an adult with aggravated murder.

Court documents filed in the case Tuesday revealed startling allegations of abuse prior to the baby's death.

Isaiah Weaver, 17, is charged with aggravated murder, a first-degree felony, in the death of 21-month-old Jaycieion Sanchez.

Because he is under 18, the charge is not eligible for the death penalty but carries a potential sentence of 25 years to life in prison, or life in prison without the possibility of parole.

He is also charged with two counts of child abuse, a second-degree felony.

At the time of his arrest, Weaver was booked into Salt Lake Valley Detention Center. Prosecutors filed a motion Wednesday seeking to transfer him to an adult facility, saying Weaver poses a threat to other juveniles at the youth facility.

Weaver had been staying with his girlfriend, the baby's mother, for about a month in the home of the baby's grandmother, according to charging documents. Because he hadn't been working for about two weeks, Weaver was in charge of taking the woman's 5-year-old child to school, then staying home with Jaycieion and another 2-year-old boy.

Shortly after noon on Jan. 16, police were called to the apartment, 4635 S. 2890 West, on a report Jaycieion was unconscious and unresponsive. Police found the baby, who was cold to the touch, lying on his back on the bathroom floor with his eyes partially open and a large bruise on his cheek, according to the charges. He was rushed to Primary Children's Hospital where he was pronounced dead.

Medical personnel later determined Jaycieion had been dead for some time before emergency responders were called, according to the charges. The baby had sustained severe head trauma; his body, head and mouth were covered in bruises; and his lower back, buttocks and the backs of his thighs were marked with lines that appeared to have been inflicted by a hard, thin object, charges state.

Jaycieion died of blunt force injury, a medical examiner determined.

An autopsy revealed damage to the muscles beneath the linear marks suggested the strikes were very hard, according to the charges, as well as head trauma indicative of being hit and shaken, bruising all over the baby's head, and injury to the baby's back.

The 5-year-old told police Weaver had been disciplining the two younger children by heating a wire hanger with a lighter and then striking them with it, the charges state. Doctors found patterns of bruising on the 2-year-old's buttocks and the back of his thighs, as well as a healing burn making a similar pattern on his chest, the charges state.

On the day Jaycieion died, surveillance footage from the 5-year-old's school recorded Weaver pushing the two younger children in a stroller while at the school from 11:09 to 11:20 a.m., according to the charges. In the video, Jaycieion's face appears discolored and the baby remains motionless, even when jostled by the other child, charges state.

The school nurse told police she had approached Weaver and the children in the stroller that day and noticed Jaycieion's color seemed off, according to the charges. The woman told Weaver he should take the baby to see a doctor, but Weaver didn't respond to the comment, the charges state.

Earlier coverage:

Teen baby sitter arrested after child dies in his care

Police booked a 17-year-old teenager into the Salt Lake Valley Detention Center after a 21-month-old child died in his care.

The woman told police Jaycieion was motionless, his cheek was cold when she touched it and she couldn't find a pulse when she checked for one, according to the charges.

The baby's mother told police that Jaycieion seemed fine when she left for work at about 7 a.m., but when she spoke with Weaver at about 9:30 a.m., he said the baby was not acting right, seemed sleepy, was sleeping with his eyes open and wasn't responsive when placed in a stroller, according to the charges.

Weaver called again about noon saying Jaycieion wasn't moving, was limp and cold, but was breathing, charges state. The mother told him to call 911 and rushed home.

After he was informed Jaycieion had died, Weaver told police he had been holding the boys on his back and spinning them over the past few days, and had been throwing them in the air, according to the charges. Weaver said the baby had hit his head on the floor a few times when he had been thrown, and on the day before the baby died, Weaver said he had thrown the baby because he wanted him to be quiet, charges state.

Weaver also said he had given the boys "a lot of spankings" on the day Jaycieion died, according to the charges. When he realized the baby wasn't breathing, Weaver said he sat with him and waited for the child's mother to call, charges state.

Weaver told police he had a bad temper and had spanked the two boys "too hard" with their clothes off the day before, leaving them with immediate welts, charges state. He also said he had hit Jaycieion in the mouth, causing it to bleed.

When he was spinning Jaycieion on the day he died, the baby lost consciousness and Weaver panicked and laid the baby down, charges state. The baby had a nosebleed after spinning, according to the charges.

"Weaver stated that once (Jaycieion) passed out, he realized he had gone too far," charges state.

A hearing on the matter is scheduled for Jan. 30.

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