Which preposition to use with bullitt

on Occurrences 2%

I do not feel, therefore, that the story is complete without at least a brief reference to my views concerning the Treaty of Versailles at the time of its delivery to the German delegates, which were imperfectly disclosed in a statement made by William C. Bullitt on September 12, 1919, at a public hearing before the Senate Committee on Foreign Relations.

during Occurrences 1%

The memorandum was first made public by Mr. William C. Bullitt during his hearing before the Senate Committee on Foreign Relations in September, 1919 (Senate Doc. 106, 66th Congress, 1st Session, pages 1177 et seq.).

Which preposition to use with  bullitt