Conversation so far:
What happened to the Taiwanese band Mayday during their hiatus?
During their hiatus, Mayday released the autobiographical documentary titled The Wings of Dream
Was the Taiwanese bands autobiographical documentary titled The Wings of Dream a bestseller?
During their hiatus, Mayday released the autobiographical documentary titled The Wings of Dream, with ticket sales hitting more than NT1.2 million in barely three days
Did the Taiwanese bands autobiographical documentary titled The Wings of Dream continue to sell at a rate more than NT1.2 million within barely three days?
What happened with the Taiwanese band Mayday's return to the music scene in 2004?
After Masa's official release from the military, the band regrouped and held their City of the Sky  concert on 16 August 2004 at the Taipei Municipal Stadium.
How many people attended the Taiwanese band Mayday's City of Sky concert?
The Taiwanese band Mayday's City of Sky concert attracted nearly 40,000 fans.

Question: Did anything major happen during the concert?
Self-contained rewrite: Did anything major happen during the Taiwanese band Mayday's City of Sky concert?