Kullander "passed away unexpectedly in his sleep" on Nov. 23, Amber said in a statement on its website on Friday. "He led by example with his intellect, generosity, humility, diligence and creativity," the firm added.

The crypto entrepreneur, nicknamed "TT," started Amber in 2017 together with a group of former finance professionals, including Goldman Sachs Group and Morgan Stanley alumni. The company, whose backers include Singaporean state investment company Temasek Holdings, was in talks to raise about $100 million, Bloomberg reported earlier this month (although in light of recent events those plans have likely been put on hold).

As Bloomberg notes, five of Amber's founders - Kullander, Michael Wu, Wayne Huo, Tony He and Luke Li - previously worked together on Morgan Stanley's fixed-income trading floor in Hong Kong.

Kullander was survived by his wife and son, according to the statement.