I start the Ring-a-Ding-Ding quest later on, and begin my journey from Boulder City to New Vegas. It was only when I got to the Grup n' Gulp rest stop that they appeared.
5 Legion Assassins appear from the other side of the bridge. At first I was glad, as Legion assassins usually have good gear. It was only mid-fight that I noticed Fitz and Lupe had joined the fight. I watched the bullet enter Lupe's skull. In a rage, I ran up to the Centurion responsible and mutilated his body with my super sledge. I used a knife to behead and and held it in the air as a token of my victory. Or so I thought.
In a corner of the overpass, a cowardly vexillarius stood, pistol in hand. He didn't waste any time putting a bullet between Fitz's eyes. By the time I noticed him, it was too late.