Picheni - a union delegate - was abducted on 16 December, 1976, and taken to the ESMA. He recounted that there, he was beaten on several occasions for moving his hood in order to see, tortured with electricity, subjected to a mock execution, and witnessed a fellow prisoner beaten to death. He was freed in January 1977 but lived in fear for the rest of the dictatorship as he continued to receive menacing phone calls.
Of course, it is not for me to say exactly why Picheni killed himself or why now, but it's surely a reminder that some wounds run very deep.
ESMA: se suicidó uno de los testigos (Tiempo Argentino via Espacio Memoria)