Creepy

[Neapolitan Ice Cream]

Something just triggered the burglar alarm downstairs. No sign of false entry. Strange.

 

[ncc1701]

Power surge maybe, that sometimes happen with our hard wired smoke detectors .

 

[Poohlove]

We used to have that happen from time to time, it turned out to be that the motion sensor needed replacing.

 

[mel&me]

We used to have that happen from time to time, it turned out to be that the motion sensor needed replacing.

Yep. Bad motion sensors can do this.
Happens all the time with motion sensor lights also.
They turn on for no reason.