How did Orson wells create panic amount radio listeners in 1938?

Orson Welles was a famous actor, director, and producer in film, television, and radio in the early half of the 20th century. In 1938, he did a special Halloween broadcast of H. G. Welles famous science fiction novel 'War of the Worlds' which depicted a Mars invasion of Earth. The one hour drama started with news reports of certain activity on Mars, followed by news reports of Martian invasion of Earth that sounded so authentic and professional, that it caused mass hysteria amongst those listening to the broadcast.