86 300zx Alarm going off???

[1986_300zxpat]

Hello, I've just purchased an 86 300zx and early this morning, about 8 AM, the alarm went off. Normally, I wouldn't be concerned about the issue besides the fact that my car was covered, and about 30 ft. from the nearest road (I live in a quiet neighborhood anyways). The only thing that I can think of is that my cat jumped on it and set it off because she had only been let out at 7:45. But then I researched the factory alarm system and found out that the only way the alarm can go off is by the door being opened from the inside...(OR hood, hatch, etc) So either Houdini tried to steal my car (It's literally right outside my bedroom window the sound nearly made me s***), or there was a short in the system or something...... Every electrical component on the car works smoothly.....

[AZ-ZBum]

http://www.az-zbum.com/information.factory.alarm.shtml