Dear Friend:
IF Charles R. Ettner was a circa 1930s police officer, then most likely, he would have been around 20 years of age. That's only as a guess. If that is true, then he would have been born around 1910.
A good place to start if you have not already done so, is to look on
Free People Search by ZabaSearch! with the many, many Ettner family members listed on that web site.
In particular, there are a number of those family members around Gurnee, IL - - Lincolnshire, IL - - and Marengo, IL. But in reality, they are also listed all over the U.S.
Through this method, perhaps you will locate a long lost family member who knows something about your missing person.
Carter Glass,
Wheaton, IL