I expected the band to come in person to announce the postponement or whatever. There would not have been a riot then, since the fans would believe them. But no one gives a damn what a third party says.
The bad arrangement is also to blame, lack of security and staff. As it is said that Metallica was not happy with the arrangements.
The fans who have sold an arm and a leg for the ticket, and who have travelled long distances to reach the venue and waited for hours for the show to begin deserve some courtesy. No wonder they were all pissed.
Besides DNA had organized Iron Maiden's Mumbai concert (The one in Flight 666) without any glitches.