Natural causes. If they hadn't been counting votes, they'd have died doing something else. The number of people involved was high enough for a few hundred deaths to be expected: https://news.ycombinator.com/item?id=19773386
Automation has saved a lot of lives in other areas so it would make sense that this would also be the case in this instance. Whether removing the human factor from the democratic process is a good idea is a different debate entirely.
I don't consider myself a "techno-libertarian", whatever that means.