Oh wow, hope everyone & everything is/was okay.
The presence of original Signature Series detectors (SIGA-PS) indicates that it was installed sometime before the original Signature Series was discontinued supposedly around the early 2010s (& subsequently replaced with first the Signature II Series & then the current Signature Optica Series).
Do you recall the exact message script? I can’t make it out in the video you took of it because of all the noise.