The bad news just gets worse for Elon Musk, whose design chief smashed what was described as a bulletproof, unbreakable window at the unveiling of Tesla’s cyber truck this week. “It is literally bulletproof to a 9mm handgun,” Musk said as Franz von Holzhausen smashed a metal ball into the driver’s side window, shattering it. “It didn’t go through, that’s the plus side,” he then quipped as von Holzhausen tried it again, causing a second shatter. Forbes reports that fail sent shares in Tesla plummeting 6 percent, sinking Musk’s net worth by $768 million in a single day. The inventor is still worth $20 billion, so no need to feel too sorry for him just yet.