Yahoo News carries a Reuters story about missteps by the Ferguson, Missouri, police department in the face of riots there last summer. Most recent Census estimates place the Ferguson population at 21,111 - not tiny, but not very big.
How many police forces of towns that size are prepared and practiced in dealing with massive civil disobedience and violence? Darned few, I'll wager. Mostly they deal with traffic management and property crimes.
"Missteps" are exactly what you'd expect from a small town police department faced with riots prodded by outside agitators, happening under national media scrutiny. Such forces typically are not cutting edge models of law enforcement professionalism. They keep the peace under normal circumstances; what Ferguson faced was far from normal.