Which preposition to use with commissaire

at Occurrences 2%

le Commissaire at once; that we had only come to inspect the concentration camp of German and Belgian prisoners, and that we were leaving town that day.

of Occurrences 1%

In the month of September, 1870, he was appointed by the Government of the National Defence, Commissaire of Police, but having taken part in the insurrection of the 31st of October, he was, on the following day, dismissed from office.

Which preposition to use with  commissaire