In mid-2375, Ilario was assigned to Deep Space 9, where he quickly grew to admire his fellow officers, especially of Doctor Julian Bashir and Chief Miles O'Brien. Likewise, Ilario was well liked by the crew, and was notably observed by Ezri Dax to be intelligent, dedicated, and eager to please.
Shortly after the his arrival on the station, Ilario was quickly assigned to his first mission on board the USS Defiant, where he served as helmsman during a week long mission, successfully piloting the ship in battle against six Jem'Hadar attack ships, which were destroyed. After this astounding victory, the crew of Deep Space 9 held a celebration for Ilario at Quark's, where was able to experience his first taste of real Saurian brandy, a beverage which he knew to be a favorite of Captain Sisko.
During the celebration, he requested that he be allowed to participate in a holosuite program with Bashir and O'Brien, but they rejected his request as they valued their time on the holosuite together, assuring him that it was nothing personal. Ilario then commenced with drinking heavy amounts of brandy, along with Kira Nerys and Dax for over an hour, not wanting the celebration to end. He was eventually escorted to his quarters by Dax.
Upon entering his quarters, he grabbed a photograph of he and two of his Academy friends and proceeded to display his pride at his achievement and his wish that his friends could have seen him fight the Jem'Hadar. When Dax tried to leave, the single Ilario attempted to flirt with her, who although flattered, shrugged off his attempt and left. Dax would prove to be the last person to see Ilario alive as later that night, Ilario, who had only been assigned to the station for ten days, was murdered by an individual using the TR-116 rifle.
Following the discovery of his death, Bashir and O'Brien discussed the situation with Dax, expressing their dismay in not letting him join them in the holosuite; Dax shared these sentiments as well, regretting having left his quarters so soon. Both Bashir and Dax, who were deeply disturbed by his murder and unable to sleep, sat with Ilario in the wardroom as he rested in his photon torpedo casket.
The subsequent investigation conducted by Dax, which was not concluded until two more murders had been committed, revealed that the murderer was a Vulcan science officer named Chu'lak, who killed Ilario and the others because they possessed photographs in their quarters of people showing emotion, but more simply because "logic demanded it." (DS9: "Field of Fire")