Kagan was a starfleet officer assigned to internal affairs.
He accompanied Luther Sloan, who in reality was a member of Section 31, to Deep Space Nine, during the investigation of Dr. Bashir. Bashir was accused of being a Dominion spy. When Bashir was arrested, Kagan escorted him to a holding cell and was outraged at Bashir. He said that he was a member of the &th Fleet and had lost many good firends. (TNG: Inquisition)