Pierce County prosecutors say 40-year-old Robin Ross left her 9-month old and her 2-year old in the care of their 14-year-old brother on the evening of Nov. 30.
While Ross was allegedly out smoking crack, the 14-year-old -- referred to as C.J. in court papers -- assaulted the infant, according to prosecutors.
When Ross returned home the next morning, she found the infant unresponsive and called 911. Doctors soon learned the child had suffered severe head trauma. Doctors told investigators the boy is 80 percent brain dead and likely will not survive the injuries.
Police soon interviewed C.J., who allegedly told them he was jealous of and doesn't like his infant brother. He said while he was babysitting the kids, the infant spit on him and started crying. He said that made him angry, so he hit the boy with a rubber ball and a pillow and then violently shook him, according to prosecutors.
C.J. said he realized he'd injured the baby, but didn't call 911 because he didn't know his address and was scared he'd get in trouble.
Ross said C.J. has a history of anger problems and has been violent in the past. In fact, just a few weeks prior to the Nov. 30 incident, Ross said C.J. held a knife to his 10-year-old brother's neck, prosecutors said. In an interview with police, the 10-year-old said C.J. had punched him, choked him, and hit him with a bat in the past.
Prosecutors say Ross was well aware of those violent incidents, yet chose to leave her infant in C.J.'s care.
C.J. has been charged in juvenile court with first degree assault.