https://techcrunch.com/2019/11/25/elon-musk-says-sledgehammering-cybertruck-led-to-the-onstage-window-failure/

After pounding the side of his new Cybertruck with a sledgehammer with not a mark left behind, Elon Musk turned his focus to the “Tesla Armor Glass”.

As we all saw, the glass did not fare so well. A toss of a steel ball into the window caused it to splinter, catching everyone on stage off guard. “Oh my [bleeping] God,” said Musk.