A high-profile prosecutor reaped stock gains worth 3.7 billion won ($3.23 million) last year, then offered to resign amid growing public suspicion over the weekend. He posted the highest in 2015 wealth growth among the nation’s 2,300 ranking officials, who were subject to private property disclosure.

Jin Kyung-jun, a senior prosecutor of the Korea Immigration Service at the Ministry of Justice, had bought some unlisted shares of local mobile game developer Nexon. He took gains by selling about 800,000 shares after Nexon was listed on a Japanese bourse.

Aside from last year’s gains of 3.7 billion won, Jin reportedly enjoyed collective gains of more than 10 billion won by trading Nexon stocks over the past decade.

Jin has rejected any negative allegation in a statement. He argued that the investment opportunity had been initially offered to a friend of his, who sought shared the opportunity with many of his own friends including Jin.

The Justice Ministry also appears to have downplayed suspicions among the public. Its official was quoted by a news provider as saying that Jin “has internally verified how he came to buy and sell the stocks.”

There is a possibility that his equities trading was not relevant to his status as a high-ranking civil servant or prosecutor. Nevertheless, there is a need for Jin and the ministry to resolve the allegations.

Jin had served for the Korea Financial Intelligence Unit, an investigative arm of the Financial Services Commission, as a division leader. He had also been in charge of the department for finance and taxation probe at the Seoul Central District Prosecutors’ Office.

The FSC, to which the prosecutor had been dispatched, is the nation’s top financial regulator, and its KFIU could easily access a variety of low-key information. FSC investigators should look into whether Jin had exploited corporate insider information on Nexon. The same sort of reviews are necessary for the Seoul Central District Prosecutors’ Office.

Stock traders engaged in any irregular use of insider information could be subject to criminal punishment.

The Justice Ministry official reportedly clarified that it seems that Jin “decided to quit as he feels the ongoing controversy may undermine the reputation of the Justice Ministry and the prosecution.”

Like the ministry official’s remarks, it is a matter of credibility of the criminal investigative agency and code of conduct as a ranking civil servant. So the ministry has an obligation to launch an official probe on him in close coordination with financial regulators.

Jin has also told reporters that he would sincerely cooperate with any investigation, if necessary, by submitting all related documents as of an ordinary citizen. It is welcome to see his confident position at the present stage.

The prosecutor tendering his resignation is not a solution. He should settle the problems he created in the civil service and the capital market.