Following a fraud accusation by a short firm and potential probe by the US Securities Exchange Commission (SEC), Nikola founder Trevor Milton is stepping down as executive chairman. “Nikola is truly in my blood and always will be, and the focus should be on the Company and its world-changing mission, not me,” Milton said in a statement (via the Financial Times). “So I made the difficult decision to approach the Board and volunteer to step aside as Executive Chairman.”

Former vice-chairman of General Motors and Nikola board member Stephen Girsky will take his place, the company said. GM recently sealed a billion-dollar deal with Nikola to supply it with batteries, fuel cells and other parts. GM will also build the “Badger” hydrogen-powered pickup truck for Nikola.

Nikola has developed electric semi-trucks, along with the Badger and other zero-emissions vehicles. The company also plans to develop hydrogen-fueling infrastructure. However, it was recently accused of “intricate fraud” by a short-seller called Hindenberg Research, reportedly prompting a probe by the US Department of Justice and the SEC. Nikola has denied the accusations, calling them “false and misleading.”