Hi guys, long time reader, first post... and here we go

Bought truck used, it has an aftermarket alarm in it that Ii have no clue about, trucks been sitting dead for a few months due to some issues related to brakes which are fixed now.

Anyway, got her started up she sat there idle for about 30 min or so(letting battery get some juice) I hop in and the darn thing dies out, no power at all, aftermarket alarm starts going off, fob no worky so I take the terminals off and I hear another alarm going off... wtf right? no battery and there's an alarm going off, how is this possible? is this a factory alarm?

So I hook the terms back up and bam, aftermarket picks right back up, out of frustration(long story) I say to heck with this aftermarket and clip the wires just to shut it up so i can try to dig without annoyance. Meanwhile at the legion of doom... the other alarm starts right back in, pull terms again and it just keeps going..

I'm getting no lights inside, no power at all.. at this point i have no idea what else to include, please ask me questions.. brain fried right now but I'm sure I can answer any diag questions you may have.

Any thoughts, suggestions?

Thank you in advance.