The suspect, 35-year-old Binh Thai Luc, is charged with five counts of murder with special circumstances.
Police now tell ABC7 News the murder weapon was a hammer. They claim Luc also used a sharp edged weapon to partially sever at least one of the victims' hands.
In March, two men and three women, all members of the same family, were bludgeoned to death in the home on Howth Street, near City College.
Luc has pleaded not guilty in the case.