A 4-month-old baby boy died in a Pittsburgh hospital on Saturday after he was brought in with four days earlier with signs of severe trauma.

The baby’s father, 28-year-old Seth Williams, was charged with aggravated assault and endangering the welfare of children before the infant’s death, but a Pittsburgh Police spokesperson told the Pittsburgh Post-Gazette that “additional charges are expected” now that the child has died.

The baby was identified by the medical examiner as Micaiah Williams.

A criminal complaint says that officers were called to UPMC Children’s Hospital of Pittsburgh on Tuesday after the mother brought the boy to West Penn Hospital “in grave condition” with severe head injuries. The child was transferred to the children’s hospital, where a doctor catalogued “four distinct skull fractures,” as well as significant bruising, dead brain tissue, broken bones, and other severe injuries.

The doctor said the injuries could not have come from a fall and that the baby was unlikely to survive the severity.

The baby’s mother, Aleah Ostruh, told police that in addition to Micaiah, she has 4-year-old twins with Williams. She said she left all three children with Williams on Monday when she went to work and that he later called her and told her the twins had knocked over the boy’s bassinet and he had fallen.

Ostruh rushed back home and “found the house in disarray.” She went out and bought medicine to treat the boy in the night, but by morning he had worsened. She walked him to nearby West Penn Hospital, she told investigators, but before she arrived he stopped breathing.

Another witness, said to be Seth Williams’ father, told police that his son called him on Monday and asked him to take the kids because they were acting out. He went to the apartment, he said, and found broken glass on the floor and a door pulled off its hinges with holes in it.

His son told him the twins caused the damage, but the elder Williams told police “there was no way that two four-year-old kids could do that much damage,” the complaint said.

“Witness #1 (Seth Williams’ father) said he then spoke to the (twins) and asked them what happened. Witness #1 said that Victim #2 told him that his/her dad, Seth punched him/her in the head and that his/her head hurts,” the complaint said. The other twin said Williams threw him/her across the room.

Both twins showed signs of abuse, police said.

Police initially responded to the hospital and then went to the couple’s apartment to collect evidence. They found Williams hiding in the basement and arrested him on an outstanding warrant and probation violations.

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[Featured image: Seth Williams/Allegheny County Jail]