I'm in NW Arkansas and got a hit on this one today; same frequency, same NAC but didn't sound like TSA. Nearly an hour of surveillance at a house and tracking a vehicle on I-10 westbound at exit 46D (that's near Gulf Port, MS). At one point, someone came up on freq and identified as "the Fort Smith office" and asked who was operating on this net. Reply said they were from the Gulf Port, Mississippi, office. All signals were full-quieting at my location near Springdale.
Seems like a band opening getting into the NW Arkansas repeater (which may explain it being heard in Joplin before). But, what agency?