While the purpose of the letter was ostensibly to warn citizens to be careful when carrying a firearm especially in encounters with police, I think the true purpose of the letter was to complain about the great unwashed, i.e., you and me, being allowed to carry concealed.
His letter brought this response from "Emthree":
I appreciate the difficult work performed by law enforcement officers in this country. But when an officer reaches the point where his concern for personal safety does not permit him to recognize the Constitutional rights of other Americans, it's time to find a new line of work.
I could not have said it better myself.