The simulation was conducted Sunday from 8 a.m. to 6 p.m.
According to police, the drill involved a simulated active threat inside the tower as well as simulated injuries and simulated gunfire throughout the event.
There was a large presence of emergency service personnel and vehicles in the area. City, state and federal law enforcement officers were present during the drill, police said.
The drill shut down several streets downtown.
All streets surrounding 10 S Dearborn Avenue were closed Sunday from 1- 4 p.m.
See the list of street closures below:
- Dearborn - Madison to Monroe
- Clark - Madison to Monroe
- Madison - Clark to Dearborn
- Monroe - Clark to Dearborn