A high-ranking Los Angeles County Sheriff’s Department official announced his retirement Tuesday after an internal investigation was opened into his purchase of a stolen Audi sedan from a tow-yard owner with a department contract, reports the Los Angeles Times .

Assistant Sheriff Michael Rothans, 53, is two years from the age when he would have maximized his county retirement benefits.

The investigation began on Oct. 1 after The Times inquired about Rothans’ purchase of the car. The probe is expected to continue despite Rothans' retirement.

In an email to Sheriff's Department executives, Rothans said he is retiring on Oct. 26 because of long-term health issues "that have recently been exacerbated and need to be addressed."

Rothans bought the Audi A4, which he believed to be a 2010 model, for $3,000 last May from Lisa Vernola, who owns Vernola’s Towing in Norwalk.

Rothans has said he did not believe the purchase was unethical because he bought the car from Vernola, not her tow company. Because she was a friend, he said, he did not ask about the car’s history and did not know the car was one step removed from her impound lot.

In fact, the car was a 2012 Audi A4 that had been stolen new from a dealership in Mission Viejo. Rothans and Vernola said they had no idea the car was stolen. Sheriff's officials are prohibited from purchasing property that has been seized by the department.