LOS ANGELES (CBSLA) — Two 18-year-olds have been charged with murder in connection with the fatal beating of a counselor at a South Los Angeles children and family services facility, the Los Angeles County District Attorney’s Office announced Wednesday.

Nyier Mason and Keith Lewis both face one count of murder for their alleged participation in the Jan. 2 beating of 25-year-old David McKnight-Hillman at Wayfinder Family Services. McKnight-Hillman later died as a result of his injuries.

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“We all grieve for David McKnight-Hillman and his family,” District Attorney George Gascón said. “As prosecutors, we will fulfill our constitutional duty to hold accountable the people responsible for his murder and offer the assistance of our Bureau of Victim Services to help his family obtain the support and services they need to address their loss and heal from the effects of their crime-induced trauma.”

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Lewis plead not guilty to the charge and is scheduled back in court Feb. 4. Mason is scheduled to be arraigned Thursday. Both are being held in lieu of $2 million bail. If convicted as charged, they face a possible maximum sentence of 15 years to life in state prison.

Four male youths, ages 16 and 17, have also been charged with one count of murder in juvenile court. All four denied the charge Wednesday and are scheduled to return to court Feb. 4.

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The Los Angeles County Sheriff’s Department was said to be continuing its investigation.