Prosecutors: Fitchburg man allegedly killed Jeremiah Oliver after boy told him to stop hurting mom

FITCHBURG — Alberto Sierra Jr allegedly killed the 5-year-old boy whose body was found in a toolbag along a highway in Sterling after the child asked him to stop hurting his mother, prosecutors revealed in court Friday.

Prosecutors say Sierra and his then-girlfriend Elsa Oliver were in the midst of a physical altercation in September 2013 when Jeremiah Oliver approached Sierra. Jeremiah, who was living and sleeping in a kitchen closet at the time due to perceived behavioral issues, allegedly told Sierra “Don’t hurt my mommy” after the Fitchburg man headbutted the boy’s mother.

Sierra then allegedly grabbed Jeremiah’s head and slammed it against the floor. Prosecutors told Judge Karin Bell that Sierra placed Oliver, who was not moving, back into the closet area.

The next day, Jeremiah was not breathing, prosecutors said. This allegedly prompted Sierra and Elsa Oliver to dispose of the body.

Jeremiah was reported missing after his sister told Fitchburg school officials that Sierra was abusing the children and she had not seen her brother for weeks.

Assistant District Attorney Courtney Lynn Sans outlined that Sierra allegedly repeatedly moved Jeremiah’s body. She says Sierra first removed the body once he became aware that officials may have become aware of Jeremiah’s disappearance.

She detailed that the bag in which Jeremiah’s body was eventually found on the side of Interstate 190 in Sterling was owned by Sierra. Family members allegedly saw Sierra, a mechanic, use the bag to transport his tools to work.

Sierra appeared to lose strength in his knees while his defense attorney argued that Sierra would benefit from a release on probation to care for his advanced case of rheumatoid arthritis.

The Office of the Chief Medical Examiner determined Jeremiah’s death to be a homicide and listed the cause of death as “homicidal violence of undetermined etiology.”

Prosecutors, Fitchburg police, and state police detectives assigned to the DA’s office continued working the case, and on Wednesday, May 17, announced the additional murder charge against Sierra.

In 2017, Sierra pleaded guilty to three counts of assault and battery with a dangerous weapon, two counts of assault and battery, and two counts of reckless endangerment of a child. The seven charges stemmed from incidents involving his girlfriend, Elsa Oliver, and two of her three kids. He was sentenced to six to seven years in state prison with three years of probation.

Elsa pleaded guilty to assault and battery and two counts of reckless endangerment of a child in August 2017.

Jeremiah’s death led to intense scrutiny of the Department of Children and Families. A caseworker had been assigned to the Oliver family and the worker hadn’t noticed Jeremiah was missing for several months.

Sierra was held without bail Friday on charges of murder and disinterment of a body. He is next due to appear in court on June 28 for a pretrial conference.

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