John E. Jones III, president of Dickinson College (PA) and the former chief judge of the U.S. Middle District Court of Pennsylvania, writes:  I am a college president. And I am afraid. The mass killing last week in the college town of Lewiston, Maine, is the 36th this year in the United States, according to an AP/USA Today/Northeastern University mass killings database. The 18 who were murdered bring us to a total of nearly 200 victims of these ghastly events.  Sadly, it is easy to predict that there will be more of them before the year is out. Which community — college town or not — will bear the weight of the next tragedy?