Riley Aldrin Shepard was a Human man. Shepard was a Red Squad cadet.
In 2372, Shepard was a member of the Red Squad cadet team that sabotaged Earth's Division of Planetary Operations. Benjamin Sisko learned that Leyton was behind the action when he questioned Shepard. (DS9 episode: "Paradise Lost")
Just before the start of the Dominion War, Shepard was assigned to the USS Valiant. Tim Watters took command when the officers were killed and for the next year the Valiant crew operated freely, attacking Dominion vessels. When the ship went up against a Jem'Hadar battleship, Shepard was killed. (DS9 episode: "Valiant")
Shepard was posthumously awarded the Drakon Cluster of Courage. (DS9 - Strange New Worlds III short story: "Dorian's Diary")