The Siren Board

So I'm in Richmond VA, and I start hearing this siren around 12 am. I go to investigate, and its a truck, rolling around the parking lot of the Kroger. It didn't have any visible siren, but the siren was definitely coming from it. No one here seems to know. I couldn't get a very good look at it, because the moment I showed up, it left. I think there was something like "Hi-Tech" on the side of it, but I googled it and can't find anything about it. It looked like a large pickup truck, with a slanted back, and what looked to be an exhaust pipe coming out of the top. Can anyone help identify this for me and explain its purpose?

Parking lot vacuum, maybe? Those things sure sound like a siren, and nearly as loud...

Charles

I googled it, and yes that is exactly what it was! Thanks so much.