2011 Dodge Caliber - Factory alarm system will not shut off

We have a 2011 Dodge Caliber, the other day I pressed the unlock button on the key fob and the doors unlocked, but when I opened the driver side door the alarm began to go off. I pressed the unlock button again thinking that would make it stop. It didnt. I tried closing the door and pressing the lock button thinking it would lock and I could just unlock it again. The alaram still did not shut off. I pressed the panic buttom twice and it only changed the pitch of the horn and the pattern in which it honked. Finally after pressing any and all buttons in a panic because it would not stop the horn just blared constantly, as if someone had their hand held down on the horn. My husband finally disconnected the battery and it stopped. We left it overnight disconnected thinking that would be plenty of time to "reset" the alarm. The moment he reconnected the  batter it did it again. He can start the car and drive it but the alarm just continues to go off. He finally just disconnedted the horn but again it's still going off, lights flashing but no sound. How in the heck do you fix this? I am afraid to take it to the dealership as it's going to cost a fortune in labor and testing etc. to correct it.