(NEXSTAR) — A mother and her boyfriend have been arrested and charged in the death of her 8-year-old son, whose skeletal remains were found inside a Houston-area apartment with his three apparently abandoned siblings.

Brian W. Coulter, the boyfriend, was charged Tuesday with murder, while the mother, Gloria Y. Williams, was charged with felony injury to a child by omission and tampering with evidence.

Officials had ruled earlier Tuesday that the child died by “homicidal violence with multiple blunt force.”

The child’s skeletal remains and the three other children were found in the apartment Sunday, authorities said.

The Harris County Sheriff’s Office said a 15-year-old had called to report his brother had been dead for a year and was inside the home. The teen told authorities that his deceased brother was in the room next to his.

Deputies found the body as well as the teen and two other siblings ages 10 and 7.

Sheriff Ed Gonzalez, who called the case “horrific” and “heartbreaking,” said the children appeared malnourished and “showed signs of physical injury.”

The sheriff said it appears the surviving children were fending for each other and that the parents had not lived in the apartment for several months.

“May the deceased child Rest In Peace,” Gonzalez said in a statement. “May the other children receive the love, healing, and support they need and deserve.”

The children’s mother and her boyfriend are both in custody, but it was unclear if they had attorneys.

The Associated Press contributed to this report.