Smith did not share details of how Sandoval contracted the virus or when he was hospitalized. In January, the U.S. Attorney for the Northern District of Illinois, John Lausch, said that Sandoval, 56, had agreed "to testify on any matter" as part of his plea. 

Sandoval was expected to face as much as 12 years in federal prison, but his cooperation would have brought a lighter sentence. In a November court filing, prosecutors said Sandoval had been providing "valuable cooperation that is expected to last at least several more months." 

In addition to the investigations of asphalt supply companies RAS Southwind and Bluff City Materials, Sandoval also was believed to be cooperating with federal prosecutors investigating a red light camera operator, Safespeed. He had been recorded asking for a "protector fee" from the company.

In a statement, Sandoval's family said it had “unexpectedly lost the center of our family today. Marty was larger than life with an enormous heart and an endless devotion to us. We’re proud of his legacy, miss him already and know he joins his four siblings and parents in a better place all too soon." The statement was attributed to his wife, Marina Sandoval, and children Angie, Jenny and Martin Jr.