DuPont, ex-employee plead not guilty, denying negligence in deadly LaPorte plant disaster FacebookTwitterEmail 1of30 The DuPont company and a former employee pleaded not guilty in a chemical disaster that killed four workers. Robert Tisnado, 39, and Gilbert "Gibby" Tisnado, 48, who died in a hazardous chemical leak at a DuPont plant in La Porte last week Friday, Nov. 21, 2014, in Pasadena. ( Johnny Hanson / Houston Chronicle )Johnny Hanson, Staff / Houston ChronicleShow MoreShow Less 2of30 DuPont employees and brothers, Robert Tisnado, left, 39 and Gilbert "Gibby" Tisnado, right, 48, died in ...