Employer rescinds offer before intern starts but after a signed contract

I'm a fresh grad and just got devastating news that the company I was supposed to start full-time tomorrow as an intern had undergone some "changes in business priorities and compliance requirements" and must "rescind the offer".

I'm really stuck on what to do because I was going to be financially dependent on this job. The contract was all signed, the start date was already pushed back by a week due to a background check from 1st Dec to the upcoming 7th Dec then I just received an email at 4a.m on Saturday about the news (the HR that informed me operates in the US).

I had replied to the HR, subtly reminding them that a signed agreement already had been made and they replied back with "sorry" and "thank you for understanding" and nothing about pay for the notice period.

I haven't been in a situation like this before and it's mentally exhausting and I really want to ask redditors what they know about employment and what I should do and not do.