Chicago police officials say they were briefed last Wednesday about the al-Qaida terror threat that has prompted government travel warnings and 21 embassy closings around the world. That was 48 hours before the State Department put out its public alert.
The Chicago briefing resulted in additional security at the Lollapalooza music festival, and authorities say more police attention was given to well-known landmarks.
As the music played in Grant Park over the weekend, Chicago police were reacting to a different sound: al-Qaida chatter from overseas that U.S. Homeland Security officials told them indicated an attack somewhere was coming.
"We ramped up the bag searches to insure that everybody was getting searched with the bags coming in and out. I don't even know what the total number of bag searches was, but it was overwhelming," said Chicago Police Supt. Garry McCarthy.
McCarthy says there were more undercover officers in the crowd and bomb dogs on the perimeter-brought in once Chicago police were told of the terror plot, "it was going to be big and strategically significant."
"Even though they feel its focused on embassies abroad. With Lollapalooza here we had to take some extra steps. We did. We're thankful that nothing happened. But it doesn't mean were satisfied that we can move on yet," said McCarthy.
This may be why: clues in the calendar that suggest al-Qaida on the Arabian Peninsula may be targeting August 7, which this year is the last day of Ramadan, the Muslim holy season; the 15th anniversary of the deadly East Africa embassy bombings and the 23rd anniversary of Operation Desert Shield, after Iraq invaded Kuwait.
For U.S. officials, the concern is "surgically implanted devices... Bombs put in terrorist's bodies," technology developed in Yemen. "These are the guys who have developed the techniques to defeat our detection methods."
Former Chicago Police Supt. and ABC7 public safety consultant Jody Weis says the unknown may be whether such an implanted miniature power source, circuitry and detonator could get through airport security. Weis said he's not aware of testing done to determine whether routine procedures would work.
"If you put a bomb inside of a human body, the only bit of metal is going to be the blasting cap or the initiator. I'm curious if that would be picked up through the conventional screening process," Weis said.
ABC News is reporting that U.S. intelligence includes al-Qaida communications with someone in the U.S.