Sara Ann Concannon was 18 months old when she died in February, a few days after her mother's live-in boyfriend called paramedics to say the baby had lost consciousness.
The boyfriend, David Arthur Malloy, 20, first told police that Sara had fallen at their home in Pasadena, authorities said.
He was arrested Sunday and charged with murder in the death of the baby. Prosecutors say it is an apparent case of shaken baby syndrome.
An autopsy by the state medical examiner found that Sara died of multiple injuries to the chest and head, including at least two skull fractures, prosecutors said yesterday.
"We believe it's a shaken baby case," said Frank R. Weathersbee, state's attorney for Anne Arundel County. "The injuries are those that would result from severe shaking of a child."
Malloy was arrested Sunday night at a relative's house in Pasadena, two days after a county grand jury indicted him on charges of second-degree murder, manslaughter and child abuse in the girl's death.
The indictment was sealed until a District Court hearing yesterday during which Judge Robert C. Wilcox ordered Malloy held without bail at the Anne Arundel County Detention Center.
Prosecutors and police declined to say what might have motivated Malloy. In many cases involving infants with similar injuries, including several in recent years in Howard and Baltimore counties, a caretaker was found to have shaken the baby violently in frustration at being unable to stop the baby's crying.
According to the National Center on Shaken Baby Syndrome, a baby can suffer serious brain damage from being shaken forcefully for as little as 20 seconds.
Malloy has not entered a plea, and prosecutors said yesterday that he did not have a lawyer. A woman who answered the phone at his family's house yesterday said "no comment" and hung up.
A year before her death, Sara made headlines as the beneficiary of a spectacular rescue from a burning building.
She was 6 months old in February last year when a cigarette set her mother's duplex, in the 3500 block of Brickwall Lane, on fire.
Three construction workers saw smoke and rushed to the house. Sara's mother, Christal Hayden, then 19, who worked at a McDonald's restaurant, dropped her baby from a second-floor window into their arms.
The next month, County Executive Janet S. Owens and Fire Chief Roger C. Simonds gave the workers citations at a public ceremony.
Prosecutors said Malloy was baby-sitting Sara on Feb. 18 at the Pasadena duplex while Hayden was at work. That afternoon, he called authorities to say that Sara had fallen and lost consciousness.
Sara was taken to Johns Hopkins Hospital, where she died three days later.
Police immediately labeled the death suspicious. Assistant State's Attorney Michael Cogan said yesterday that Malloy later told police he had shaken Sara. His statements to police and the autopsy led to the review by the grand jury that indicted him Friday.
Sara's uncle, Stephen Hayden, said yesterday that his family would have no comment on Malloy's arrest.