A security guard for the New York Racing Association was arrested and charged with theft in the third degree Monday for stealing mail returned to the NYRA that contained mutuel vouchers worth up to $10,000.Henderson Kirton admitted Monday to trying to redeem the returned mutuel vouchers the NYRA had mailed out in conjunction with its Mystery Mutuel Voucher promotion Friday. One of the vouchers from the returned envelopes contained the $10,000 grand prize. NYRA employees are expressly prohibited from participating in NYRA promotions. Kirton was immediately fired upon his arrest.The U.S. Postal Inspector's Office and the New York State Racing and Wagering Board have also been notified of the arrest and are reviewing the case to determine if additional charges may be brought against Kirton.