Not very friendly buses

We were out walking in San Francisco when we saw flashing lights and police cars and Muni trucks.  Upon getting a bit closer, we found that two buses had not played nice together:

Seemed like quite a mess.  

A little later in the day, we were in Union Square and we saw one of the buses on the back of a really big tow truck:

One commenter is asserting that the driver of the bus on the right parked the bus to get some coffee, and the bus rolled backwards, sideswiping the other bus and knocking over several items on the sidewalk.

Not a great day for Muni.