He got up in the middle of the night to get a drink and while carrying his glass of water, tripped and fell down the stairs.
He shattered his cheekbone, sliced his eye socket and cut the nerves of his left eye.
He laid there unconscious and "almost bled to death," SAP cofounder and chairman Hasso Plattner told German publication Wirtschafts Woche.
Fortunately, someone did find him. But he lost his left eye in the accident.
McDermott has already talked to Sueddeutsche Zeitung, another German media outlet, about the accident. He said such a thing "can happen to anyone" and that the lesson is that "it's important to stand back up again, if you fall down."
He also says that the most important thing is "I'm still alive."
He's been working through his recovery and is expected return to SAP's headquarters in Germany when doctors to allow him to fly in October.
A SAP spokesperson told Business Insider:
In July, SAP informed employees that CEO Bill McDermott sustained an injury at a relative’s house. Unfortunately, we have recently learned that as a result of the injury, Bill lost his left eye. However, during this time his ability to lead SAP was never affected. Bill is expected in Germany next month where he will meet customers and employees. We wish him a speedy recovery.
McDermott's horrific accident is another chapter in a rather epic life, which he wrote about in a book last year. He worked his way out of poverty and up the ranks to run the SAP one of the world's largest software companies.