Signal Flares Fired — Massacre Begins (~6:10 PM)

Two green signal flares are fired from a helicopter overhead at approximately 6:10 PM, signaling the start of the operation. Snipers from the Olympia Battalion begin firing from buildings overlooking the plaza — including the Chihuahua building — into both the crowd and the surrounding army units. The army, believing it is being attacked, opens fire on the protesters. Witnesses describe soldiers firing indiscriminately into the crowd for 30 to 90 minutes.