It's still unclear exactly what happened to the boy.
Banning Police say whatever happened probably occurred at the Banning residence of the boy's stepfather, 24-year-old Andrew Payne, last Monday.
Both Payne and the boy's mother, 20-year-old Davia James, were held in Robert Presley Detention Center in Riverside after the boy died over the weekend.
Police say Payne and James made a number of inconsistent statements.
Chief Leonard Purvis says they waited two days to call authorities about the injuries.
"When this child, or any child, experiences any type of head trauma, any type of injury, you call right away, and that's what is so suspicious about this case is they waited two days," said Purvis. "God knows what they were thinking, what they were planning, but this child suffered."
The boy was taken to San Gorgonio Memorial Hospital. Police say he had a fractured skull, a punctured lung, a lacerated liver and possibly lacerated kidneys as well.
"Some very severe brutality basically against this young 2-year-old child," said Purvis.
Police say it's possible Payne, the stepfather, was under the influence at the time of the alleged crimes. He was arrested on a felony charge of child cruelty causing death.
Banning Police said murder charges would be filed with the district attorney.
Davia James was arrested on a felony charge of failure to seek medical care.
If you have information about the case, contact Banning Police at (951) 849-1194.