Aaron Handy had been watching the boy at his girlfriend's home on Peppertree Way on Aug. 20. When the boy's mother came home, she found the child unresponsive.
According to Antioch police, Handy allegedly tried to convince the mother not to call 911 for her child and then fled her home.
The boy was flown by helicopter to a hospital to be treated for a traumatic brain injury.
Doctors put him in a medically induced coma and removed a portion of his skull to alleviate swelling in the brain, police said.
Police said he was out of the coma today, but doctors were still evaluating his brain injury.
Investigators believe that the injury was caused by an abusive forceful action of Handy's and was not an accident, police said.
On Wednesday, police arrested Handy at a home in Stockton. He allegedly later confessed that he had injured the boy in anger, police said.
Handy is being held at the West County Detention Facility in Richmond on suspicion of felony child abuse. His bail has been set at $100,000, according to a county jail official.
The Contra Costa County District Attorney's Office is expected to review the case Monday and make a decision about whether to file formal charges, police said.
Anyone with information about the case is asked to call Detective Robert Green at (925) 779-6932.