During his first court appearance Monday, Jake Musga entered court in a so-called suicide smock and kept his gaze on the ground.
"The jail has him classified a certain way and he's wearing certain clothes to protect himself from himself," said prosecutor Phil Sorensen.
Tacoma police arrested the 19-year-old at a high-rise apartment on Saturday. Investigators believe Musga hurt his girlfriend's 2-year-old son inside one of the units. The child died a short time later from blunt force trauma to his head and stomach, the Pierce County Medical Examiner's office said.
Musga's Facebook page is filled with photos from his football career at Arlington High School, but in court Monday, prosecutors hinted at Musga's recent run-ins with the law.
Prosecutors say last year, a Snohomish County court convicted Musga of violating a restraining order in a domestic violence situation.
Musga is not the dead child's father -- he was babysitting the boy while the mother visited relatives. Prosecutors are not giving any other details about the case until charges are filed, which is expected to happen by Wednesday.
In the meantime, the judge ruled Musga be held on $1.5 million bail.