Alarm/Dash Lights Flashing after months in storage, won't crank
 

I tried to start my '03 after a couple of months in storage, but the alarm won't turn off even when unlocking with the fob. The horn constantly beeps and the dash lights are constantly flashing. The engine won't crank. Replaced the battery temporarily from another car and it's the same issue. While not in use, I had the battery disconnected the entire time. Any advice?