The relief that Osama bin Laden is gone is being tempered by the realization that his death at the hands of the U.S. military could create a retaliatory attack.
Chicago officials are preparing for the worst, noticeably increasing security at the city's airports, houses of worship and on the streets.
The Chicago Police Department placed all plain-clothes police officers in full uniform Monday until further notice.
Extra emphasis was placed on monitoring critical infrastructure Monday at the operations center of the Chicago Office of Emergency Management and Communications, home to the hub of the city's extensive surveillance camera network.
Terrorism experts say Chicago has long been on Al-Qaeda's wish list.
"Chicago does present a greater retaliatory threat than the average city in the United States," said Robert Pape, Director of the Chicago Project on Security and Terrorism. "It's because we have very famous buildings in Chicago."
Fans arriving to the Bulls playoff game at the United Center Monday night noticed immediate changes, as the NBA mandated metal detector screenings for the rest of the playoffs. Fans didn't seem to mind.
"I'd rather be safe than sorry. I wouldn't want any retaliation in a building for the game," Crest Hill's Mike Jacksa said before the game.
Chicago's synagogues have been on high alert since 9/11, but in light of bin Laden's death, area Jewish institutions received a security alert from the Anti-Defamation League calling for a review of safety procedures.
"We're asking them to be aware of their surroundings. To make sure all security cameras are working. That all employees are aware of what the security precautions are in place," said Jenna Benn, Assistant Director of the Greater Chicago Chapter of the ADL. "Al-Qaeda has been motivated by anti-Semitism and anti-Zionism."