Horn Honks when reconnecting battery

I got home yesterday from work, realized I needed to run to the store, only to find my truck wouldn't start 5 minutes after I'd shut it off. It acted like the battery was dead so I went to Autozone and picked up a new Duralast Gold battery for it.

When I hooked up the terminals, the stayed on and never stopped until I disconnected teh battery. The odd part is that is not the main battery connection that is doing it. Its a second line that connects to the positive terminal.

I'm at a loss as to what is causing this and could use some suggestions besides towing it to the dealership.

 

did you try ur remote? and turning it off. it does that when reconneting back the cables.

 

Alarm system... Press the lock button on the remote.