Last October, Tesla-doubting investors were out in force short-selling shares in anticipation that Elon Musk would sell a large chunk of his own stock to fund his purchase of Twitter. At the time, many suspected the billionaire had maxed out the amount of money Tesla would allow him to borrow using a pledge of his shares as security.

Little did they know he had another source to raise money that could potentially be used to fund his $44 billion deal.

According to documents reviewed by the Wall Street Journal, the serial entrepreneur hit SpaceX up for a $1 billion bridge loan in the same month the Twitter deal went through—this time collateralized by a portion of his 42% stake in the commercial spacefarer.

Dearth of options

While Musk repaid the cash the very next month, such a loan is not common in the corporate world, and most robust boards would frown on such a practice from a governance perspective.

For one thing, SpaceX has its own priorities—chief among them, enabling a multi-planetary society. Musk himself dreams of establishing a permanent colony on Mars and—since he is no believer in longevity—one day dying on the Red Planet.

Diverting cash from a company that only a year before risked bankruptcy in order for its boss to potentially privately pursue unrelated business endeavors would be highly unorthodox.

The loan revelations brought to light by the Journal come one month after the sudden and unceremonious replacement of Zachary Kirkhorn, Tesla’s highly respected head of finance, for which there has yet to be a explanation.

SpaceX did not respond to a request by Fortune for comment, while Tesla could not be reached for a statement.

When it came to the pending Twitter deal, however, Musk likely did not have that many attractive options from which to choose.

By early October 2022, it seemed clear a Delaware court would follow precedent and compel the tech tycoon to abide by his word by paying Twitter shareholders $54.20 for each share.

Front-running Elon Musk’s Tesla sales

Musk succeeded in raising $13 billion in debt from lenders and another $7.1 billion in equity from wealthy investors. But the visionary CEO still had to pitch in another $26 billion of his own money, once banker and legal fees were included.

Judging by previous regulatory filings, Musk hadn’t dumped enough Tesla stock to afford the acquisition and would have to liquidate more to close the gap.

Assuming he was still short an estimated $5 billion, short-sellers believed they could anticipate his next move and front-run his trade, selling shares before Musk could and buying them back on the cheap after the price dropped.

As bears began the countdown toward the court-imposed Oct. 28 deadline to consummate the deal, they had reason to believe they had him in their sights.

Hoping to boost the stock price, Musk used a Tesla Q3 call that month to suggest investors could expect their company would become the world’s first $4.5 trillion corporate megacap, worth more than Apple and Saudi oil giant Aramco combined.

Speculators weren’t influenced by the timing of his sudden optimism, however, and the stock continued to underperform as short-sellers placed their bets.

Tesla bears waited in October for Tesla to file the Form 4 disclosures proving Musk had offloaded more shares. But those disclosures didn’t arrive.

Theories subsequently were bandied about, often revolving around one of the banks underwriting the Twitter deal, Morgan Stanley for example, giving Musk a bridge loan in order to secure fees and bonuses linked to the successful completion of the purchase.

Yet it appears that, unbeknownst to speculators, he may have borrowed at least part of the money he needed from SpaceX to avoid further pressure on Tesla shares.

About a week after the Twitter transaction closed on Oct. 27, Tesla then revealed Musk had sold some 19 million shares worth close to $4 billion in early November, which is when he paid back the SpaceX loan. By then, it was too late for the short-sellers.