On the night of Friday, November 16, 1973, police forces started confronting the thousands of protestors gathered inside and outside the Polytechnic campus, located on Patission Street, one of the busiest in Athens. Komnenos was one of the many high school students barricaded inside the Polytechnic. At about 10:00 pm, the police used guns and smoke-bombs to evacuate the streets from the protestors. At the time, Komnenos had joined other students on the corner of September 3rd St. and Averof St., exactly across from the Polytechnic. The students were reportedly hit by sniper fire from the roofs of the neighbouring buildings. Komnenos was killed at 10:15 p.m. when a bullet pierced his heart. His torn shirt is exhibited at the memorial of the victims of the Polytechnic uprising and was held by Hortensia Allende to wipe her tears, during her visit there.
Diomedes Komnenos is considered by many a heroic symbol of the Athens Polytechnic uprising. The student uprising is credited for helping trigger the eventual collapse of the military regime which ruled Greece since April 21, 1967. Nevertheless, the Polytechnic uprising was used as a pretext by junta hardliner Brigadier Dimitrios Ioannides to overthrow George Papadopoulos on November 25, 1973 and to put and end to a "liberalisation process" headed by Spiros Markezinis. The Ioannidis regime collapsed on July 1974 following the escalation of events in Cyprus that led to metapolitefsi.