A Fitchburg mother and her boyfriend have been arrested in connection with the disappearance of her 5-year-old son, authorities said.
Elsa Oliver, 28, and her boyfriend, Alberto L. Sierra, 22, are facing multiple charges in the disappearance of Jeremiah Oliver, Worcester District Attorney Joseph D. Early Jr. said.
“We are treating this as a potential homicide,” Early said Monday. Sierra was charged with attacking Jeremiah and one of his young siblings with a knife, Early said. Oliver was charged as an accessory after the fact to the attacks and two counts of reckless endangerment of a child, he said.
Jeremiah was last seen by family members on Sept. 14, prosecutors said, but Early’s office was not notified of his disappearance until officials from the Reingold Elementary School reported the child missing Friday.
Early said it was unclear why Jeremiah was not reported missing for nearly three months. A spokesman for the Fitchburg Public Schools could not be reached for comment Monday evening.
Authorities, who have issued public alerts for the missing boy, say Jeremiah is 3 feet 4 inches tall, weighs about 40 pounds, and has brown hair and brown eyes.
“When we were notified, the State Police detectives assigned to my office and Fitchburg police immediately got involved,” Early said. “There were interviews done, and a search warrant was executed at the Kimball Street address where the child was known to live.”
As a result of the search warrant, Sierra was arrested over the weekend, and Oliver was arrested Monday, Early said.
A judge ordered Oliver to produce her missing son in court, Early said. By Monday evening, she had failed to do so. Oliver will face a contempt hearing later this week, Early said, at which point she could be held indefinitely until the order to produce Jeremiah is met.
Sierra, who is from Fitchburg, was charged with two counts of assault and battery with a dangerous weapon and two counts of assault and battery on a child causing bodily injury, Early’s office said. He pleaded not guilty at his arraignment in Fitchburg District Court Monday and is being held without bail pending a dangerousness hearing, which is scheduled for Thursday.
Oliver is being held on $5,000 bail and is scheduled to be arraigned Tuesday in Fitchburg District Court. Oliver’s two other young children have been placed in the custody of the state Department of Children and Families, Early’s office and the department said.
A spokeswoman said the department is working with police, but did not address questions about past involvement with the family.
Nicholas Jacques can be reached at nicholas.jacques@