If it wasn't done by the US government this is terrorism pure and simple, going by what the people in your source said:

>"We were tired of attacks from government-backed hackers on the United States and other countries," someone in control of an email address left in the note told Motherboard Saturday... "We simply wanted to send a message...." In addition to disabling the equipment, the hackers left a note on affected machines, according to screenshots and photographs shared on social media: "Don't mess with our elections," along with an image of an American flag...