Schabowski’s Press Conference
At a live press conference, SED Politburo spokesman Günter Schabowski mistakenly announced that new exit rules took effect “immediately”. East Berliners rushed to the checkpoints, and that night the Wall opened.

Bundesarchiv, Bild 183-1989-1109-030 / Thomas Lehmann · CC BY-SA 3.0 de · Source
Cornered by the exodus and the protests, the East German leadership drew up new rules on 9 November 1989 allowing citizens to travel or emigrate to the West on application. They were meant to take effect the next day, but Schabowski, poorly briefed, read out the note near the end of a live evening press conference at the International Press Centre in East Berlin and, asked when the rules applied, replied: “As far as I know, immediately.”
When West German television reported that East Germany had opened its border, huge numbers of East Berliners crowded to the checkpoints. Lacking orders, the guards at Bornholmer Straße opened the gate around 11.30 p.m., and the other crossings soon followed.