<human>: This happened in New York, USA

I resigned from my previous job on June 15th and received paychecks on June 15th, June 30th, and July 15th. On July 15th I was concerned that this payment was in error. I contacted the HR/accounting person who was responsible for paychecks and they told me everything was legit and the check I received on July 15th was for my final days and my remaining PTO(this conversation happened over Lync IM so is in writing/archived). 

A week later I received an email from the president of the company stating that I had been paid in error and needed to sign a document so they could withdraw the checks from June 30th and July 15th from my bank account. I countered with the fact that I was told by the HR person that this money is mine and I am not going to sign anything to give the money back, especially if mistakes were made on their end.

Currently, I heard the HR person has been let go over this ordeal and the president is still sending me emails/calling my cell explaining the money is not mine and they are trying to handle this professionally before elevating this to the "next level". Should I be concerned? Do they have any legal standing to make a case against me? The amount in question is less than $2500.

Can you summarize the given text in a few sentences?
<bot>: Quit a job, they paid me for an extra month, I confirmed with them it was fine, later they try to recover said money. Do I need to worry about any legal retribution?