DECATUR, GA — A man suspected in the deaths of two siblings in DeKalb County is now in custody.

DeKalb County Police confirm that 25-year-old Steven Christopher Mathis was arrested by Henry County police and is now being held at the DeKalb County Jail on murder charges.

The investigation began Monday night after officers found a man and woman dead inside an apartment at the East Perimeter Pointe Apartments in Decatur.

The DeKalb Medical Examiner has identified the victims as 34-year-old Christopher Lewis and 32-year-old Brandi Lewis, a brother and sister.

Police believe the killings were domestic-related, but the investigation remains open and active as they work to determine a motive.