LOS ANGELES (CBSLA.com) — A 44-year-old Hawthorne man was officially charged Wednesday with the murder of his girlfriend’s 14-month-old son.

Julio Mejia, 44, pleaded not guilty to one count each of murder and assault on a child causing death.

The toddler was rushed to Centinela Freeman Regional Center about 11:15 p.m. Sunday from the apartment the boy lived with his mother, three more of her children and Mejia.

The boy, identified only as Bryan C., was not breathing when he arrived at the hospital. He was pronounced dead about a half hour later.

Bryan C. suffered from blunt force trauma, authorities said.

Mejia — who is not Bryan C.’s biological father — was arrested early Monday and faces 25 years to life in prison if convicted.

He remains jailed in lieu of $1 million bail.

Meija’s next appearance at the Airport Branch Courthouse in Los Angeles is scheduled for September 17.

Sandra Cartagena, Meija’s 42-year-old girlfriend, was arrested on suspicion of child endangerment. The District Attorney’s Office has declined to file a case against her, citing insufficient evidence, according to a spokeswoman for the office.