Nikola announced early Monday that founder Trevor Milton is voluntarily stepping down from his roles as executive chairman and a member of its board. The resignation came 10 days after a short-selling firm accused the company of making "an Ocean of Lies."
The stock, which has had volatile swings, plunged 30% in premarket trading Monday. They recovered some of the losses after the opening bell.
"It's a dark day for Nikola," Wedbush analyst Dan Ives told CNBC's Andrew Ross Sorkin in a "Squawk Box" interview. "Let's call it like it is. Trevor leaving. I mean he's a key part of the vision."
The electric truck maker said the board accepted Milton's resignation, adding that Stephen Girsky, former vice chairman of General Motors and a member of Nikola's board, has been appointed chairman of the board, effective immediately.
"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. "So I made the difficult decision to approach the Board and volunteer to step aside as Executive Chairman. Founding Nikola and growing it into a company that will change transportation for the better and help protect our world's climate has been an incredible honor."
In a Sept. 10 report, titled "Nikola: How to Parlay An Ocean of Lies Into a Partnership With the Largest Auto OEM in America," short-selling firm Hindenburg Research accused Nikola of making false statements about Nikola's technology in order to grow and secure partnerships with auto companies, including General Motors. GM stock was down more than 4% in early trading Monday.
The Securities and Exchange Commission and Department of Justice are reportedly investigating claims that the company misled investors.
Nikola pushed back on the Hindenburg accusations, saying there were "dozens" of inaccurate allegations in the report.
In an early Monday tweet, Milton said, "I intend to defend myself against false allegations leveled against me by outside detractors."
GM recently took a 11% stake in the company and said it will produce Nikola's marquee hydrogen fuel cell electric pickup truck the Badger by the end of 2022. Last week, GM CEO Mary Barra said the automaker conducted "appropriate diligence" regarding a $2 billion deal with the electric vehicle start-up.
In a statement, GM said it will work with Nikola to close the deal "to seize the growth opportunities in broader markets with our Hydrotec fuel cell and Ultium battery systems, and to engineer and build the Nikola Badger.
It added: "Nikola, Honda and other companies who are looking to GM’s technology as a platform for their products, represent just one part of our overall EV strategy. Our overall goal is to put everyone in an EV and accelerate adoption."
"This is a gut punch to the story," Wedbush's Ives told CNBC, "and definitely I think a white-knuckle period right here for Nikola bulls."
Nikola stock has been wildly volatile this year, rising from $13 at the beginning of May to a current 52-week high of $93.99 in June. The Nasdaq-traded shares finished Friday at $34.19.
The company's average volume over the last 10 trading days has come in at 53.2 million shares, though it has only about 361 million shares outstanding.
Nikola CEOÂ Mark Russell said the company remains committed to its objectives and creating value for shareholders.
"Our priorities remain unchanged and, in collaboration with our partners, we are laser-focused on executing on our strategic initiatives and laying the groundwork to become a vertically integrated zero-emissions transportation solutions provider," Russell said in a statement.