A former aide whose report of possible embezzlement led to a secret investigation of Gov. Scott Walker's Milwaukee County executive staff has died.

Thomas Nardelli was 70.

He was Walker's chief of staff when Walker was county executive and followed him to Madison when Walker became governor. Nardelli left a position as administrator for the state's Division of Environmental and Regulatory Services in 2011.

Walker described Nardelli in a statement as "a wonderful public servant and a dear friend."

Walker's spokeswoman Jocelyn Webster said Tuesday that Walker learned of the death Monday night from Nardelli's widow.

Nardelli was working for Walker when he alerted the Milwaukee County district attorney's office that money had been taken from a veterans fund. That led to a secret investigation that ended with multiple convictions.