The Lead Masks Case

On August 20, 1966, two Brazilian electronic technicians, Manoel Pereira da Cruz and Miguel José Viana were found dead on the Morro do Vintém (Vintém Hill) in Niterói, Rio de Janeiro. Both wore lead masks that's were the case got its name because no one really knows why or how did they die. Was it a suicide? A murder? Or something entirely different? Over 50 years and the case is still unsolved.