Authorities discovered a note and documents that relate to former auto dealer Denny Hecker after his former father-in-law fatally shot himself in his car last week, according to newly unsealed court papers.

Bill Prohofsky, 71, of Minnetonka, shot himself March 3 in his Volvo while the car was parked in an empty lot in Medina, authorities determined. He died the next day. Prohofsky was the stepfather of Hecker's fourth wife and had worked in Hecker's former auto business. Before his death, Prohofsky had been accused of helping Hecker try to hide at least $81,557 from the court presiding over Hecker's bankruptcy.

Court papers filed late Wednesday said Prohofsky was carrying a note for investigators, and a key to a Wells Fargo safe-deposit box was found in his wallet. His car contained a laptop computer and a briefcase of documents. Medina police seized the items.

According to an FBI affidavit relating to the search warrant of Prohofsky's Volvo, police opened the briefcase and "observed documents that appeared to relate to Hecker's concealment of assets."

Prohofsky's note mentioned a safe-deposit box at Central Bank and "indicated that [he] intended to help the [FBI] investigation'' of Hecker, according to the affidavit.

Investigators questioned Prohofsky on March 2 about two safe-deposit boxes at Central Bank but were told that he was not hiding assets. The note and documents he left behind suggest otherwise, authorities said.

Hecker, once the largest auto dealer in the state, filed for bankruptcy June 4, claiming $767 million in debt and $18.5 million in assets. He has been charged by a federal grand jury on 25 counts of bankruptcy fraud, wire fraud, money laundering and conspiracy. Hecker has denied wrongdoing.

According to the warrant, the FBI searched Prohofsky's safe deposit box at a Wells Fargo branch and found an envelope with $10,000 in cash labeled "2009 Money for Taxes," various e-mails and a copy of a check related to Hecker's Jacob Holdings St. Cloud LLC. The box also held a memo regarding a rental firm, bankruptcy documents and the lease for Hecker's Jacob Holdings of Crosslake property where Prohofsky lived last year.

The trustee in the Hecker bankruptcy case sued Prohofsky last month, accusing him of hiding $81,557 of Hecker's money in Prohofsky's own Wells Fargo Bank account.

Prohofsky said in a deposition last month that Hecker instructed him to pay bills with the money. Prohofsky shot himself one week after being sued.

Staff writer James Walsh contributed to this report. Dee DePass • 612-673-7725