It's a little confusing between store manager, supervisor, general manager, etc. If I understand correctly, the person you complained about fired you, rather than the person you complained to.
If that is the case, and the person you complained TO has the ability to straighten this out, fire the guilty and reinstate you, the innocent, they should do so, ASAP.
If I got it wrong, or if the person you complained TO is unable or unwilling to take appropriate action, you can act, as follows:
1) Apply for unemployment insurance tomorrow. It is retroactive only to the date you apply. If you are denied, appeal. You may need a lawyer to appeal.
2) Although MA is an "at will" state (you can quit whenever you want, and they can let you go when ever they want, for any legal reason or no reason at all) they seem to have fired you for improper reasons including whistle-blowing and reporting of sexual harassment (you are being treated unfairly because you did NOT engage in sex with the Store Manager). Accordingly, you may have a discrimination claim at MCAD and/or EEOC as well as a wrongful termination claim. These claims may carry punitive damages and attorney fees, as well as back pay, emotional distress damages, etc. You should consult a lawyer experienced in these areas (not my strong suit) as soon as possible. Most will consult at no charge. Use this site's Find-A-Lawyer, "Employment Law".
The foregoing answer does not establish an attorney client relationship, is not confidential, and should not be relied upon in place of an actual consultation with an attorney. Mr. Boone is licensed to practice in Massachusetts, before the U.S. Tax Court, and the Federal District Court of Massachusetts. Most initial consultations are free. Further information is available on my profile and at www.boonehenkofflaw.com.
It is illegal to retaliate against an employee who reports sexual harassment. It is difficult to follow all the "players" in the fact pattern you describe. I am not sure what you are talking about with videos and cameras.
To make a claim for illegal retaliation, the employee has to show: (1) she filed a complaint; (2) the person who retaliated against her knew about this complaint; (2) the employee then was subject to an adverse employment action like a suspension, termination, transfer, a bad performance review, or a job warning; (3) a causal connection exists between 1 and 2.
The employee can show a causal connection by direct evidence: Drop this sexual harassment complaint or I will fire you. If there is no direct evidence, circumstantial evidence is admissible. For example, if there is a close period of time between the employee’s complaint and the negative job action, this can be proof of discrimination under a theory known as “close temporal proximity.” I know, that sounds like a Star Trek term. But, it’s much simpler than that. It just means that retaliation can be inferred from the close time between the complaint and the adverse action.
This information should not be construed to be formal legal advice nor the formation of a lawyer/client relationship.