Not my video!
http://www.youtube.com/watch?v=MwTBUwlq9WU
Seems like a Whelen was malfunctioning like the ones I've recorded. It tries to talk and start in some signal and fails. Then it goes off in wail, cuts out, and goes to the gas protection tone (the first time I’ve heard an actual siren use it on yt).
It sounds like there may be a couple of Whelens, 2001s, and a STL-10 in the mix, although that STL-10 might be a 2001 about to die.
I bet it sounded creepier in person.