WORCESTER, Mass. — A Massachusetts man is headed to prison for assaulting the siblings and mother of a 5-year-old boy whose body was discovered three years ago in a suitcase off a highway.

Alberto Sierra was sentenced Tuesday to six to seven years in prison after pleading guilty to assault and child endangerment charges in Worcester Superior Court.

Prosecutors say the 26-year-old man assaulted Jeremiah Oliver’s mother and two of his young siblings between March and December in 2013. Jeremiah had been missing since late 2013 when his remains were found off Interstate 190 in Sterling in 2014. No one has been charged in his death.

Oliver’s mother — Sierra’s former girlfriend — is awaiting trial on assault and reckless endangerment charges related to the alleged abuse of her children.