Termination with no reason given by HR representative of the company

Yesterday right after lunch, the rgional manager of my company along with a HR representative entered my office and shut the door. The HR rep proceeded to say, we decided to go in a different direction concerning concerning the M&R duties you perform to today will be your last day. I queried both on the reason for my firing,(Did have a bad performance apprasial, did I violate any company policies, was there anything the could present my in writing) they both again simply stated we are going in a diferent direction, advise me of the company seperations policy, Cobra, unemployment, etc. and wanted me to sign the seperation aggreement. I stated I would take it with me and review it and respond in time. I have been there a little more than 18 months (This was a new start up venture branched off from the main core business. They offered me no severance, just a prorated portion of a bonus I was due contractually, with my company insurance expiring at the end of the month