It's a homicide.

That's the official ruling tonight from the Sacramento County Coroner in the death of a 2-year-old toddler who died while in the care of his babysitter.

The Coroner said little William Philyaw died of blunt abdominal injury and they ruled the death a homicide.

The boy was being watched by a neighbor at an apartment in the Arden Arcade area Wednesday.  His mother returned home to find him unresponsive.

"We heard her freaking out, crying, screaming like, 'my baby's dead,'" said neighbor Amber Gloria.

Gloria told News 10 the baby and his brother were being watched by another resident of their apartment complex identified only as Sam.  

A woman performed CPR to no avail, others say they noticed bruising on the two-year-old's body.  Sacramento County Sheriff's Spokeswoman Lisa Bowman said their work has been intensive, 

"Our detectives have done a complete and thorough crime scene investigation at the home.  They responded to the hospital as well."

Bowman said no arrests have been made, and child abuse investigators are on the case.