NEWPORT BEACH - A former Orange County assistant sheriff who pleaded guilty to filing false tax returns and then cooperated with a corruption prosecution of then-Sheriff Mike Carona has died here.

The Orange County Register reported Wednesday that Don Haidl's family issued a brief statement saying he unexpectedly died Tuesday night. He was 61.

Haidl was a millionaire picked by Carona to head the Sheriff's Department's reserve program. He resigned in 2005 as his son, Greg, formerly of Rancho Cucamonga, faced charges in the rape of an unconscious 16-year-old girl. Two years later, the former assistant sheriff pleaded guilty in the tax case under a deal to cooperate in a federal probe of Carona.

Haidl wore a hidden microphone to record conversations that led to Carona's conviction for witness tampering.