Happened to me twice as well. Don’t kill him too fast, just let him say all the lines:
During the fight:
Ministry Commander Landon: These spies have had a terrible influence on you. Especially ones like this filthy, crippled charr and his flunky.
Lightbringer Tybalt Leftpaw: My name is Tybalt Leftpaw, Lightbringer of the Order of Whispers, and that’s Agent to you!
Demmi Beetlestone: Landon, you dog, tell my father that you failed. I’ll never let you capture me alive.
Ministry Commander Landon: I die… for Kryta.
It should work then.