RIVERHEAD - The man accused of violently killing his ex-girlfriend and her toddler son back in December pleaded not guilty in a Riverhead courtroom today. Prosecutors say Jerry A. Lewis stabbed 21-year-old Shakeela Planter in her Bay Shore basement apartment just days before Christmas last year. They say Lewis also fatally beat her son, 23-month-old Jaiden, in an "extremely vicious manner." According to authorities, Lewis wrapped Planter's body in plastic bags and left it on her bed. They say he stuck the infant's body inside a bag and placed it in the kitchen freezer. Prosecutors say Lewis continued to live in Planter's apartment with the bodies for at least three days before traveling to his mother's home in Maryland. There, investigators say Lewis confessed to the killings to relatives, who brought him to a local police department.Lewis pleaded not guilty to first-degree murder and was ordered held without bail. His attorney says he will likely ask for a psychological evaluation.Man accused in Bay Shore murders held without bond in MDArrest made in North Bay Shore murders of mom, toddlerPolice: Mother, child found dead in North Bay Shore