Employment Law Questions? Ask an Employment Lawyer.
Hello and welcome. My name is ***** ***** it will be my pleasure to assist you.
Generally an employer has the right to terminate employment "at will" without regard to what is fair or reasonable. There is also no legal obligation to pay any severance. So, the fact they didn't give a reason for your termination would not be unlawful and so is not something that you can use to leverage severance.
Your employer might be inclined to offer severance in exchange for a confidentiality agreement if you possess sensitive information about the company, but you cannot overtly threaten to release such information if they don't pay you money as that could be construed as extortion which is actually a crime. The most you can do is suggest that you will sign a confidentiality clause (and let them draw from that whatever conclusions they may) in exchange for a larger severance package. You need to be extremely careful here though because extortion is a serious matter.
As for the bonus, employers generally have the right to pay or not pay bonuses at their discretion. However, you could argue something called breach of the covenant of good faith and fair dealing, which is basically a principle which holds that an employer cannot unfairly deprive an employee of a benefit they could have reasonably expected from their employment, such as a bonus. It would be a very hard claim t actually win in court, but at least the threat gives you some more leverage to negotiate severance.
I hope this helps, and I wish you luck.