Given that a good 50% of the human race interacts with computers only rarely, if at all, this strikes me ridiculous hyperbole.
Let's start with people dependent on computer controlled medical equipment. Maybe kill 50% of them, but I doubt that figure is even close to a million.
Computers control the power grid, so all the power goes off. That's not going to kill anyone beyond a few random accidents, at least not immediately. The folks dependent on medical equipment are already dead for the most part.
Computers control a lot of transportation, but their going down isn't going to cause all the planes to fall out of the sky and the trains to fly off the rails. We'd get some crashes, but if that's 10,000 deaths, I'd be surprised.
Most logistics today is totally dependent on computers, so world trade screeches to a halt. Does that kill anyone? Maybe a lot of people go without food and medicine, but that doesn't automatically equal famine and plagues—the shipping industry did fine before computers were invented, and given no other choice, would likely be able to manage, if not as efficiently, without them.