Gerald T. McCaughey person sent me two 950 dl, checks by accident. Wilmington Delaware

I posted an item for sale in craiglist and a Jerald T. McCoughney bought the item and he sent me two 950 dls CIBC checks by accident from CIBC Chase Manhattan Bank Delaware 1201 Market St. Wilmington DE 19801 and told me to deduct the 350 dls for the item and send him back the remaining. So I tried to send him back the remaining of his money through paypal but he insisted that I should send it back through western union so I sent back 1542. On june 22, 2009 I received a letter from my bank saying that one of the checks was counterfeit, I called my bank and they couldn't help me, also they said that a check can be chargedback anytime during a whole year, now I'm afraid the other check might chargeback too, I run out of options. Hopefully someone will see this report and not fall for this.

Nelson
Bronx, New York
U.S.A.