alarm keeps going off.... but i dont have an alarm

[TorkDSR]

so, i cant seem to figure out what set of events sets off the built in alarm.
once i was walking out of the liquor store and reached in the window to unlock it and the horn started sounding, and one other time was in the garage. im almost 100 percent sure i didnt hit the panic button on the dash. its an 02 gmc k15oo

there's a "security" message that flashes on the message center.

any insite would be great

 

[TorkDSR]

i got the info....
if its locked for more than 5 min and the door is opened from the inside via going through an open window then the alarm goes off.

 

[az84chevy]

Yup and sometimes if you open the door without the remote the car wont start. Hit the lock but and the locks will go up and down once and then it will start.