An Auburn, WA, woman has been accused of causing severe brain injury to a 9-month-old child on Thursday, while babysitting the boy.

The 18-year-old woman was hired by the boy’s parents for a weekday schedule after she responded to an ad on Craigslist.

Court documents say that the woman told police that she had been frustrated with the boy, who did not appear to like her and was fussy.

The woman reported that one day the boy was being particularly fussy and she became so angry that she sat him down hard on the floor, causing his head to snap forward. She then roughly placed him in his playpen, where he fell backwards.

Shortly thereafter the boy began to cry before falling asleep and making strange breathing noises, at which point the woman called the police.

The child was transported to Children’s Hospital, where doctors found him to have suffered severe brain trauma.

The woman has been charged with first-degree assault of a child.