Rewatching the scene on the Wall, Laurentius is clearly hesitating. He didn't really want to resort to the massacre, but he got in too deep, and he chose to kill everyone else rather than answer to Yuyuhase and Ilberd about it later. And looking at Yuyuhase's smug smirk, he knows it, too.

Yuyuhase, on the other hand, has been upfront all along about only being in it for the money. I kinda wonder how he got talked into the final plot. Was he paid up front but couldn't get out and away before the Alliance moved in, then got caught between them, the Resistance, and the Empire with nowhere to go? Were the two of them not told about Ilberd's death being part of the plan and just had to leg it without a further plan? We'll probably never know for sure.