Arriaga was a Starfleet lieutenant who was stationed on Deep Space 9 in 2372.
In that year, he was part of Admiral Leyton's attempted coup d'etat against Jaresh-Inyo. To make it appear that cloaked Dominion starships were coming through the wormhole, Arriaga attached a subspace modulator to the wormhole relay station. This caused the wormhole to open and close at random.
The crew of the station discovered Arriaga and brought him to Earth aboard the Defiant. Realizing that Arriaga's testimony could stop his coup, Leyton sent the USS Lakota to stop them. (DS9: "Paradise Lost")