When Saw Gerrera and his Partisans planned a scouting mission to the planet Tamsye Prime, Senjax was part of the Imperial documentary crew that the group infiltrated. He conspired with Reece Tallent, a Partisan who betrayed Gerrera, and laid a trap to capture the anti-Imperial group on Tamsye Prime. After bringing Gerrera, Tallent and Jyn Erso into an empty room with a pair of stormtroopers, the Imperial officer revealed that he was was alerted by Tallent of the Partisan plans and the entire mission was a setup. Senjax's efforts went awry when Gerrera and Erso fought their way out of the two stormtroopers' grasp and held Senjax at blaster point to flee the room. To cut off the Partisan escape, Imperial forces launched an aerial strike, targeting the factory and town with plasma cannon blasts from TIE fighters, despite the presence of many civilians. Even after Gerrera escaped on a stolen Imperial shuttle, the Imperial aerial strike escalated, shooting turbolaser beams onto the planet from a Star Destroyer. The attack indiscriminately hurt Partisans, civilians and Imperial forces on the ground alike, Senjax included. He was seriously injured, incurring a long cut on the left side of his face that would leave a scar and a losing eye.
In the fallout of the attack, Senjax appeared on the HoloNet to recount the events on Tamsye Prime to the public. Rather than admit the truth of how the Imperial starships destroyed Tamsye Prime without regard to the presence of civilians or fellow Imperial personnel, Senjax lied. He claimed it was a terrorist attack by Partisans, with the goal of destroying a factory that manufactured items essential to the defense of its citizens. Though in truth several Partisans escaped, he asserted that the entire group was crushed and none survived. Senjax concluded by reassuring viewers that despite the many deaths, the Empire was working hard for their safety, pointing to the new defense budget approved by the Imperial Senate that morning. Jyn Erso, who witnessed the broadcast from a bar on Skuhl, speculated that Senjax must have been bribed or threatened to lie so thoroughly about how the Empire he loved had betrayed him.
Senjax was a handsome and tall man, with blond hair, ice-blue eyes, and pale skin. He had a chiseled face, a perfect smile of straight white teeth and a voice that exuded light-hearted, easygoing joy. His immaculate physical features were magnetic and made Jyn Erso feel like she could trust him, though she also felt like a grub herself by comparison. The events on Tamsye Prime transformed him from pretty boy to a battle scarred hero, leaving Senjax with a long scar down the left side of his face and a missing eye. His lost eye was replaced with a mechanical cybernetic implant decorated with gold.
Senjax's attitude drew other people to him. When shooting the propaganda documentary on Tamsye Prime, he made an effort to introduce himself to every individual on the press crew. He even devoted attention to protocol droids and felt it was rude to do otherwise. He loved the Empire, dedicating his career to espousing its virtues. Even after the Empire destroyed Tamsye Prime, killing numerous civilians and severely injuring Senjax in the process, he remained its loyal servant.