Police plan to step up patrols throughout the city's transit system. They have reissued security bulletins and reminded customers to remain vigilant and report anything suspicious.
"Remain vigilant and alert, but most of the folks are in uniform and the heightened alert has been heightened a little more," said Interim Supt. Terry Hillard, Chicago Police Department.
Expect to see more Chicago police in uniform around the Loop. You'll also see more officers at O'Hare International Airport and at CTA train stations around the city. Behind the scenes, the staff at the Office of Emergency Management and Communications is paying extra attention to the city's network of cameras.
"I did notice today, because I live all the way in Rogers Park, so I have seen a lot more security and more police. Good, good, let's do what we need to do," said commuter Tamara Andersen.
There is extra security at large public gatherings. Security guards at the United Center used metal detectors to screen fans attending the second-round playoff game between the Chicago Bulls and Atlanta Hawks. The same security measures are also in place at U.S. Cellular Field, where fans headed to see the White Sox are being screened.
"We're all here to have a good time. If that keeps us safer, I'm good with that," said Bulls fan Michelle Romanowski.
A Department of Homeland Security FBI memo about potential threats of retaliation says, "We assess the death of al-Qaida leader Osama bin Laden in the near term is likely to provide motivation for homeland attacks, particularly from homegrown, violent extremists seeking revenge or notoriety."
A terrorism expert says that Chicago does have a greater threat because there are so many famous buildings here. He also says al-Qaida will remain a threat as long as there are large amounts of troops in Iraq and Afghanistan.