Short answers, pulled from the story.
Ferenc Mészáros and Otto von Habsburg proposed opening the border at a ceremony in June 1989. The local organization in Sopron took over planning duties while contacts were made via Habsburg and Imre Pozsgay.
A border gate on Bratislava Road opened for three hours on the 19th of August 1989. Thousands of refugees crossed the Iron Curtain during this event which officially lasted from shortly before 3 p.m. until the gates closed.
More than six hundred East Germans fled to the West leaving their cars behind at the border that day. Only 661 people actually crossed the border despite thousands waiting further away.
In August, 8,923 people were arrested at the border with eighty percent being East Germans. On September 11, the border was officially opened and 30,000 East Germans fled to the West.
The picnic site is commemorated with a monument by sculptor Gabriela von Habsburg in Fertőrákos near Sopron. An annual commemorative ceremony is held on August 19 at the border today.