2003 Volkswagen Beetle CAR WON'T HOLD CHARGE

While driving the car home the lights on the dashboard came on engine battery and I don't recall what other one. I tried to start it later and it would turnover but not hold the charge. I t was almost like a car sounds when it floods, however there was no gas flow. The mechanic told me that the Security system was flashing and that it needed to be reset. Another said that I needed to get a key. Can you tell me what you think it may be, please and If I need to tow it to the dealer.