PITTSBURGH (AP) -- A 6-year-old Pennsylvania boy whose mother allegedly held him underwater in a bathtub died Saturday, four days after his younger brother drowned, the Allegheny County Medical Examiner's Office confirmed. The boy, Daniel Schlemmer, had been declared brain dead after authorities say he and his 3-year-old brother, Luke, were submerged underwater by their mother at their McCandless home Tuesday in western Pennsylvania. Forty-year-old Laurel Michelle Schlemmer is being held in the Allegheny County Jail without bond on criminal homicide and other charges in the death of her younger child. With Daniel's death, the charges against her are expected to be amended. County detectives say the mother told them she tried to drown both boys by sitting on them in the tub after a third son left for school. They say she told investigators she heard "crazy voices" telling her to push the boys underwater. Daniel had been on life support at a Pittsburgh hospital, according to the prosecutor's office. Schlemmer didn't speak during a short video conference earlier this week, and her attorney, Michael Machen, declined to comment afterward. Machen got court permission to have Schlemmer evaluated by a psychiatrist hired by her family. She appeared in a special vest that is designed to prevent inmates from tearing off their clothes and is on suicide watch at the jail. County detectives said Schlemmer told them she tried to drown both boys after her 7-year-old son left for school that day. Schlemmer told detectives she thought she could be a better mother to her oldest son "if the other two boys weren't around, and they would be better off in heaven," a police complaint said. She also told police she got into the tub, fully clothed, and sat on the boys because "crazy voices were telling her to push the boys down into the water." The boys' father, Mark Schlemmer, was at work at the time. Child welfare officials are scrutinizing the drowning and the family's contact with Allegheny County's Office of Children, Youth and Families. The county agency first contacted the family last year, after Schlemmer backed her van into the same two boys, according to police and her pastor. The county office determined that was an accident, according to Pennsylvania Department of Public Welfare Kait Gillis. Schlemmer faces a preliminary hearing April 11.