Hadn't run across this one before. Lots of accounts state Jennison was vicious; this letter to the editor provides an example.

"While the command of Gen Jas G Blunt to which Jennison’s regiment belonged was camped in one of the border Counties of Missouri a native in butternuts was arrested on suspicion by some of the men and brought to Blunts headquarters whore Jennison happened to be. On investigation no crime could be
charged to the man except that he was a Missourian. Jennison thought that was crime enough and wanted to hang him on general principles but Gen. Blunt decided that as there was no evidence to justify holding him and he should be turned loose. With an oath Jennison declared his intention to mark him so that he
would know the fellow the next time he caught him and before anyone could realize what he intended to do he whipped out his bowie knife grabbed the man by the ear and whacked it off."

“ON THE BORDER. Episodes of the Bitterness between Them in Kansas and Missouri”; letter to the editor from R. M. Peck. The National Tribune; Washington, D.C. July 26, 1900. Page 3, Column F.