If there is anything nefarious here (seems like it), this is the work of a foreign state actor probing our infrastructure for exploitable weaknesses and sizing up our response. I'll put my money on Russia, who has already been attacking our elections¹, energy infrastructure², social media, and spearphishing candidates and elected officials³.
They have conducted similar attacks in the past, sending out tweets and text message alerts to hundreds of people for nonexistent emergencies⁴.
[1] https://www.bloomberg.com/news/articles/2017-06-13/russian-b...
[2] https://www.washingtonpost.com/world/national-security/russi...
[3] https://www.secureworks.com/research/threat-group-4127-targe...
[4] https://mobile.nytimes.com/2015/06/07/magazine/the-agency.ht...