What do a USPS Truck, MARTA bus, ATL PD, and MARTA police all have in comon?

They've all be sitting in front of my apartment building now for at least 30 minutes or more. At first I thought it was weird when the USPS truck pulled up on the sidewalk, and then the MARTA bus pulled up behind it and just hung out for awhile. But I didn't clue in that something was actually up until I got out of the shower and they were both still there, but now accompanied by their own set of police officers and cruisers. The wonders of the city never cease to amaze me. I'm thankful I don't have to drive south on Briarcliff Rd right now or try to get in my driveway!