An Illinois man is behind bars for the death of his pregnant girlfriend after he claimed he shot her when she grabbed the gun under his pillow while he was sleeping.

Robert Pasco III, 42, stands accused of involuntary manslaughter, child endangerment causing death and three counts of misdemeanor endangering a child in the deaths of 35-year-old Edith Castrejon and their child Jesus Castrejon who died a week after his birth.

Chicago police responded shortly before 5 a.m. Jan. 16 to 5800 block of W. Newport to a shooting. Paramedics found Castrejon, who was five months pregnant, suffering from a single gunshot wound to the chest. They rushed her to the hospital where doctors delivered her baby before she died. Given just a 25% chance to live, he died when he was 7 days old. The shooting occurred as their three other children, ages 3, 4 and 7, slept in the room, cops said. They were uninjured.

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Pasco told cops he was sleeping when Castrejon grabbed a gun that was under his pillow, an arrest affidavit obtained by Chicago CBS affiliate WBBM said. Pasco reportedly said he took the gun and shot his girlfriend in the chest. He then allegedly hid the gun in a closet.

Police originally charged Pasco with gun charges as he is a felon and is unable to illegally possess a firearm. The firearm used was a ghost gun, authorities said. Ghost guns are generally untraceable as they are assembled either from a kit or other homemade components.