The US Attorney for Northern Indiana says the men bought 74 fully automatic machine guns and 92 laser sights. They are accused of falsely claiming the equipment was for use by the sheriff's department.
The three are Joseph Kumsta, Ronald Slusser and Edward Kabella. Prosecutors says they have agreed to plead guilty.
In a separate case, Lake County Coroner Thomas Philpot was charged with public corruption when he was Lake County Clerk. He is accused of misappropriating nearly $25,000 from a child support program.
