I have strong doubts that something like this would go unnoticed for so long in a city of 2 million people on a very public platform like Craigslist. March 4th, 2018 is quite literally, this Sunday.
Here in Minnesota, there have been 3 threats directed at schools that shut them down for the day. Those were spotted on social media and authorities could track their IP addresses. My point is, those were quelled before anything happened and nothing violent happened.
I smell fraud.