Union electrical workers are protesting outside the new city police headquarters because of a subcontractor on the project.
The International Brotherhood of Electrical Workers Union says Tom Ruzicka is an officer in R.E. Contracting. Ruzicka pleaded guilty in 2010 to stealing more than $100,000 from his employees' retirement accounts. He was also cited by the state in 2007 for underpaying employees.
City leaders say they can't legally remove a subcontractor from the project.
Police headquarters will move into a refurbished building in the 1900 block of Olive.
Tuesday's assaults were the latest in a series of violent incidents over the last month at Menard Correctional Center and other Illinois state prisons. Last Thursday, a Menard inmate died in what one official called suspicious circumstances.
Union officials say the violence is a result of Illinois Gov. Pat Quinn's decision to close several prisons around the state to save money.
Tuesday's assaults happened as about 200 union members marched outside the prison in the southern Illinois town of Chester. They were protesting over what they say are growing threats to their safety.
Corrections officials say the attack led to a lockdown.