>According to the most recent data from the FBI, the total crime rate in Grinnell is 2,185.9 per 100,000 people. That's -6.83% lower than the national rate of 2,346.0 per 100,000 people and 9.20% higher than the Iowa total crime rate of 2,001.7 per 100,000 people.
Also interesting to compare:
Location | Rate
--------------+-----
Grinnell, IA | 2,185
U.S. Avg. | 2,346
San Francisco | 4,938
Oakland | 6,456
The second ... shows low overall rates of crime, as of a decade ago.
Grinnell has a population < 10k. There's likely some variance over years, and there may be specific years with a large number of reported incidents. There is also the possibility of changes in reporting or enforcement, or of specific events resulting in a large number of charges.
Without more specific and detailed information, I'm going to call your initial claim largely unsupported.
Archives of the HomeSnacks link show a larger number of aggravated assault claims for a single year. What that might be based on deserves further clarification.