Having driven buses in a major city, hitting someone at an intersection or bus stop is a constant fear. People often walk out in front of you or lean out as you pull into a bus stop. Often in major cities, there are grooves formed along the curb because of the frequent stops, so the buses actually lean into the people on the sidewalk sometimes. I could imagine the suspension noise while hitting a low point in the road could mask the sound and feel of hitting someone, especially in a heavy rain.
Also, it is difficult to know which bus would be on what schedule. Buses often switch routes at a "terminal point" or use major roads to get into position. It seems quite possible that this bus was not in-service, but moving into position at the Cy-Ride lot.
And on rainy days, you often get behind schedule, so you may have some pressure to hurry a bit.