A 20-year-old man who suffered significant losses after following the advice of a South Korean investment YouTuber has allegedly stabbed the man in an act of revenge. The July 13 attack coincided with a 9% crash in the South Korean stock market — its seventh-largest dip on record.

The Chosun Daily reports that police arrested the man, known only as “Mr A,” on Tuesday on suspicion of attempted murder after he travelled to Busan’s Nam District and stabbed the victim — known as “Mr B” — multiple times in the face.

Mr A reportedly subscribed to a YouTube channel run by 40-year-old Mr B, and structured his investments based on his recommendations.

However, the investments caused Mr A to suffer significant losses.

This all took place as South Korea’s stock market, the KOSPI, was in the midst of a 9% nosedive.

Stocks representing AI giant SK Hynix and Samsung Electronics fell by 15.4% and 10.7%. Indeed, SK Hynix wiped out the gains it had made from its US debut last week.

SK Hynix wipes out US debut gain in one day of trading

As the price fell, Bull Theory reported that the leveraged retail accounts of 1.2 million Koreans triggered margin calls on July 13.

“Between 320,000 and 360,000 of them were fully liquidated by brokers, principal wiped out, and some now owe money to their brokerage,” it said.

It’s unclear what stocks Mr A invested in, and when the investments took place, but police in South Korea are reportedly preparing to probe the investor further to determine his alleged motives before seeking a warrant.

Mr B’s injuries are reported to be no longer life threatening.