i'm confused.

This morning on the way to work as I was heading west on I-94, I passed what I thought was Rosa Parks heading east on I-94. There were a million cops on motorcycles with their lights flashing, cop cars, a couple dark vans and then a big semi that I assumed carried her. But now I see that she arrived in Detroit last night. What the hell did I see? Who else would get a million cops and block traffic on a major interstate during rush hour? I'm also assuming who/whatever it is was coming from the airport into the city. Anyone?