A 3-month-old suffered brain bleeding. The man accused of shaking him was arrested.

A 3-month-old boy was being treated for brain injuries at a Tacoma hospital Tuesday, while his mother’s boyfriend was charged with first-degree child assault.

Prosecutors accuse 22-year-old Jonathon Eric Thomas Cartmell of causing the baby’s injuries, in part by shaking the child.

Cartmell pleaded not guilty at arraignment, and Superior Court Commissioner Meagan Foley set bail at $500,000.

Charging papers give this account of what happened:

Cartmell brought the child to Mary Bridge Children’s Hospital Feb. 13 and said the baby was having “seizure-like activities.”

Doctors found bleeding in the child’s brain that appeared to be at least a couple weeks old, bleeding in his brain that appeared to be new and a broken arm that was healing.

The trauma didn’t appear to be accidental, they told investigators.

Cartmell told police that he’d been watching movies with the baby, who was crying. He said he was frustrated, picked the baby up from his bassinet and threw him onto a bed.

The infant cried for a minute, went to sleep and woke up screaming about an hour later, Cartmell said.

The child’s legs were stiff and his eyes rolled back.

Cartmell later told another detective that he might have picked the child up to shake him but that he did not shake him hard.

The baby’s head went back and forth six or seven times, and the seizure happened “kinda like instantly,” he said.

He didn’t mean to hurt the baby, he said.

Cartmell also described throwing the baby on the bed about a month ago, throwing him on the couch a couple weeks ago and once grabbing him by the arm.

The baby’s mother told police Cartmell watched the baby while she worked.

She said she’d seen Cartmell get frustrated with the child but never shake him.

She said the baby’s father had physically abused her when she was pregnant and that the child had seizures at birth.

Medical professionals said an MRI didn’t show any brain bleeding when the child was born.

The boy was still at Mary Bridge Tuesday, where he needed blood drained from his brain daily and was expected to need a shunt for at least a year.

Doctors had him on medicine to prevent seizures and thought it likely that he’d have significant developmental delays from his injuries.

This story was originally published February 20, 2018 at 2:45 PM with the headline "A 3-month-old suffered brain bleeding. The man accused of shaking him was arrested.."