My car is completely dead and won't jump.

I noticed my security light was on, which happens every so often. I parked my car for about two hours, unlocked it with the keypad, the lights all flashed as they should, the interior lights were on as usual, I went to start it and all went dead...no battery dead. I locked it by hand and left it overnight. The next afternoon it started as normal. That evening it did the same thing as the previous evening...unlocked and went dead when I turned the key. Today it is still dead, it makes no difference when I tried to jump it. I am not sure if this is a security thing, a battery thing, or something else. I was wondering if you had any suggestions before I have it towed somewhere? Thank you so much !!! :)