On July 18, 1984 an armed man walked into a McDonald's restaurant in the San Diego community of San Ysidro and opened fire on customers and employees. When it was over 22 people were dead, including the gunman, and 19 others were wounded.
It was the worst mass shooting of its kind at the time and remains one of the worst mass shootings in modern U.S.history. It became known as the McDonald's Massacre.