From Halopedia, the Halo wiki
By 2548, Xavier, who had graduated from high school a few years before, was a member of the band Drowning Chromium alongside Dorian Nguyen, Hugo Chastain and Alex Linville. While Xavier and Alex played the guitar and Dorian was the QJ, Hugo was a singer. One night, the band played in the Brume-sur-Mer bomb shelter, only to have a brief interruption when the power went out all over town. After the concert ended, the band broke into an abandoned tourist house and sat around strumming their guitars until finally going home to bed shortly before dawn. The concert drew the interest of Tomas Reynés who invited the band to play on his boat the next night. Xavier texted an excited Dorian the good news as he was heading out to help his uncle Max check out the town's reactor to determine the source of the power blackout.
After finishing their first song of the concert, the band noticed that the audience was paying attention to something in the sky instead of them and discovered a weird light that quickly resolved itself into a spaceship. To the horror of the boat's passengers, they realized that the Covenant were attacking Meridian and Hugo quickly realized that the ship, an Ceudar-pattern heavy corvette, was heading towards Brume-sur-Mer. As Hugo wondered why Tomas wasn't bringing the boat back towards land, the corvette opened fire, setting the boat on fire and causing it to begin to sink before the corvette released Yanme'e to kill the passengers. Recognizing that his friends were too panicked to handle themselves in the situation, Dorian ordered them crawl backstage and find Tomas, lying that he had a plan. Dorian was able to kill one of the Covenant soldiers by hitting it with Xavier's guitar, breaking the Yanme'e's wings and sending it into the ocean, but breaking the guitar in the process. Dorian eventually jumped from the sinking boat, hoping that his friends had found Tomas who hopefully had a hidden lifeboat to take them back to Brume-sur-Mer or to Port Moyne. However, Hugo, Alex and Xavier didn't survive, presumably either killed by the Yanme'e or drowned when the boat sank.
Following his own narrow escape, Dorian was left unsure of his friends' fates. Dorian later explained to Saskia Nazari, who remembered him from the first concert, that he had been covering for his friends so they could get to safety, but was forced to run when more of the Yanme'e boarded the boat and he had to get the hell out. Dorian expressed hope that Hugo, Alex and Xavier escaped as he didn't believe the Covenant had gone backstage, but wasn't sure if they would've ended up in Port Moyne or Brume-sur-Mer. However, Dorian refused to ask Salome if they were in the bomb shelter as he didn't want to hear that they weren't.
A day after the escape of the surviving townspeople from Meridian, word came in that Hugo, Alex and Xavier were amongst those who didn't survive. Saskia and Evelyn Rousseau began knotting roses for them out of old clothing as an act of remembrance.
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