Car Alarms: 05 mustang, alarmtek, dash area

Question
My '05 Mustang has been having security system issues.  we open the door, it makes a clicking noise and then the alarm starts going off.  We hit the button under the dash, and it did no good.

Answer
I need to determine whether it's a factory alarm
issue or, if it's an aftermarket system you are
dealing with.

Is it: Headlights flashing, car horn honking
and a worded SECURITY or, ANTI-THEFT" light
in the dash flashing?
(doubtfull since none of the notes show this
car as having a factory alarm system)=FACTORY

Or,

is it: flashing parking lights,
an LED in the dash area, and a siren
going off?= AFTER MARKET

Let me know more on this to better
advise you on a course of action
to take.

Best Regards,

Robert Martin
CEO/ALARMTEK
CARALARMMAN.com