Nikola Corp. founder and Executive Chairman Trevor Milton was arrested trying to board an airplane in Phoenix. He had announced that he was stepping down as chairman after a report from a short-seller accusing the company of fraud. The company’s stock fell precipitously, dropping as low as $30 a share after trading as high as $79. “The focus should be on the company and its world-changing mission, not me. I intend to defend myself against false accusations leveled against me by outside detractors,” Milton said in a statement posted on Twitter. The short-sellers report came not long after Milton signed an agreement with General Motors that gave GM 11 percent ownership in exchange for technology and assistance getting Nikola’s first model to market. The viability of the deal is in question, and so is the future of GM’s electric pickup. Stephen Girsky, a former GM executive on Nikola’s board, is taking over as board chairman immediately.